Dr. Yongho Sohn is a Pegasus Professor and Lockheed Martin Professor of Engineering in the Department of Materials Science and Engineering, and Associate Director for Materials Characterization Facility (MCF) at University of Central Florida. MCF is a FL-state user facility for academics and industry with over $20M in analytical instrumentation and 3 full-time staff engineers.
He received his B.S. with honors and M.S. from Worcester Polytechnic Institute, Worcester, MA in mechanical and materials engineering, respectively. He graduated in 1999 with a Ph.D. in materials science and engineering from Purdue University and spent two years as a post-doctoral research scholar at the University of Connecticut. He joined University of Central Florida in 2001 as an assistant professor.
His research and teaching interests includes microstructural analysis and control, multicomponent intrinsic and interdiffusion in multiphase alloys, powder processing and additive manufacturing, thermal barrier coatings and other protective metallic/ceramic coatings, and light-weight metallic alloys and metal-matrix composites.
He has published 8 book chapters, over 175 journal papers and 60 proceedings papers. He gave over 525 presentations including 115 invited lectures at conferences around the globe. He is a Fellow of ASM International (FASM), recipient of NSF CAREER Award (2003), Outstanding Materials Engineer Award from Purdue University (2016), UCF’s 2017, 2012 and 2006 research incentive awards, UCF’s 2007 and 2013 teaching incentive award.
He is an associate editor for Journal of Phase Equilibria and Diffusion and a member of editorial board for Metallurgical and Materials Transactions. He has supervised to completion, 15 Ph.D. students, 30 M.S. students and 9 post-doctoral scholars, and currently supervises 2 post-docs, 4 Ph.D. students, 4 M.S. students, and 3 undergraduate research assistants.
Details on his research and teaching activities can be found at http://mse.ucf.edu/sohn.
"Characterization of Interaction Layer in U-Mo-X (X = Nb, Zr) and U-Nb-Zr vs. Al Diffusion Couples Annealed at 600 degrees C for 10 Hours"
Emmanuel Perez, Ashley Paz y Puente, Dennis Keiser, Yongho Sohn,
Defects and Diffusion Forum
Vol. 312-315
2011
1055-1062
Link
U-Mo has thus far proven to be one of the most feasible metallic fuel alloys for use in research and test reactors due to its high density and stability during irradiation. However, an adverse diffusional interaction can occur between the fuel alloy and the Al based matrix. This forms an interaction layer (IL) that has undesirable thermal properties and irradiation behavior leading to accelerated swelling and reduced fuel efficiency. This study focused on the effects of ternary alloying additions on the formation of IL between U based alloys and Al. Diffusion couples of U-8Mo-3Nb, U-7Mo-6Zr, and U-10Nb-4Zr (wt.%) vs. pure Al were assembled and annealed at 600 Degrees C for 10 hours. Both thickness and phase constituent analyses were performed via electron microscopy. The major phase constituent of the IL was determined to be the UAl3 intermetallic compound. The Nb and Zr alloying additions did not reduce growth rate of IL (1.3-1.4 m/sec1/2) as compared to couples made between binary U-Mo and Al (0.9-1.8 m/sec1/2).
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"Diffusion Barrier Selection from Refractory Metals (Zr, Mo and Nb) via Interdiffusion Investigation for U-Mo RERTR Fuel Alloy"
Ke Huang, Dennis Keiser, Catherine Kammerer, Yongho Sohn,
Journal of Phase Equilibria and Diffusion
Vol. 35
2014
146-156
Link
U-Mo alloys are being developed as low enrichment monolithic fuel under the Reduced Enrichment for Research and Test Reactor (RERTR) program. Diffusional interactions between the U-Mo fuel alloy and Al-alloy cladding within the monolithic fuel plate construct necessitate incorporation of a barrier layer. Fundamentally, a diffusion barrier candidate must have good thermal conductivity, high melting point, minimal metallurgical interaction, and good irradiation performance. Refractory metals, Zr, Mo, and Nb are considered based on their physical properties, and the diffusion behavior must be carefully examined first with U-Mo fuel alloy. Solid-to-solid U-10 wt.%Mo versus Mo, Zr, or Nb diffusion couples were assembled and annealed at 600, 700, 800, 900 and 1000 °C for various times. The interdiffusion microstructures and chemical composition were examined via scanning electron microscopy and electron probe microanalysis, respectively. For all three systems, the growth rate of interdiffusion zone were calculated at 1000, 900 and 800 °C under the assumption of parabolic growth, and calculated for lower temperature of 700, 600 and 500 °C according to Arrhenius relationship. The growth rate was determined to be about 103 times slower for Zr, 105 times slower for Mo and 106 times slower for Nb, than the growth rates reported for the interaction between the U-Mo fuel alloy and pure Al or Al-Si cladding alloys. Zr, however was selected as the barrier metal due to a concern for thermo-mechanical behavior of UMo/Nb interface observed from diffusion couples, and for ductile-to-brittle transition of Mo near room temperature.
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"Diffusion under temperature gradient: A phase-field model study"
Rashmi Mohanty, Jonathan Guyer, Yongho Sohn,
Journal of Applied Physics
Vol. 106
2009
Link
A diffuse interface model was devised and employed to investigate the effect of thermotransport (a.k.a., thermomigration) process in single-phase and multi-phase alloys of a binary system. Simulation results show that an applied temperature gradient can cause significant redistribution of constituent elements and phases in the alloy. The magnitude and the direction of the redistribution depend on the initial composition, the atomic mobility and the heat of transport of the respective elements. In multi-phase alloys, the thermomigration effect can cause the formation of single-element rich phases at the cold and hot ends of the alloy (i.e., demixing). |
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"Diffusional Interaction between U-10wt.%Zr and Fe at 903 K, 923 K, and 953 K (630 C, 650 C, and 680 C)"
Keqin Huang, Young Joo Park, Ashley Paz y Puente, H. S. Lee, Bulent Sencer, Rory Kennedy, Yongho Sohn,
Metallurgical and Materials Transactions A
Vol. 46
2014
Link
U-Zr metallic fuels cladded in Fe-alloys are being considered for application in an advanced sodium-cooled fast reactor that can recycle the U-Zr fuels and minimize the long-lived actinide waste. To understand the complex fuel-cladding chemical interaction between the U-Zr metallic fuels with Fe-alloys, a systematic multicomponent diffusion study was carried out using solid-to-solid diffusion couples. The U-10 wt pct Zr vs pure Fe diffusion couples were assembled and annealed at temperatures, 903 K, 923 K, and 953 K (630 °C, 650 °C, and 680 °C) for 96 hours. Development of microstructure, phase constituents, and compositions developed during the thermal anneals were examined by scanning electron microscopy, transmission electron microscopy, and X-ray energy dispersive spectroscopy. Complex microstructure consisting of several layers that include phases such as U6Fe, UFe2, ZrFe2, a-U, ß-U, Zr-precipitates, ?, ?, and ? were observed. Multi-phase layers were grouped based on phase constituents and microstructure, and the layer thicknesses were measured to calculate the growth constant and activation energy. The local average compositions through the interaction layer were systematically determined, and employed to construct semi-quantitative diffusion paths on isothermal U-Zr-Fe ternary phase diagrams at respective temperatures. The diffusion paths were examined to qualitatively estimate the diffusional behavior of individual components and their interactions. Furthermore, selected area electron diffraction analyses were carried out to determine, for the first time, the exact crystal structure and composition of ?, ?, and ?-phases. The ?, ?, and ?-phases were identified as Pnma(62) Fe(Zr,U), I4/mcm(140) Fe(Zr,U)2, and P42/mnm(136) U3(Zr,Fe), respectively.
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"Effects of Cr and Ni on Interdiffusion and Reaction between U and Fe-Cr-Ni Alloys"
Ke Huang, Young Joo Park, Le Zhou, Yongho Sohn, Kevin Coffey, Bulent Sencer, Rory Kennedy,
Journal of Nuclear Materials
Vol. 451
2014
372-378
Link
Metallic U-alloy fuel cladded in steel has been examined for high temperature fast reactor technology wherein the fuel cladding chemical interaction is a challenge that requires a fundamental and quantitative understanding. In order to study the fundamental diffusional interactions between U with Fe and the alloying effect of Cr and Ni, solid-to-solid diffusion couples were assembled between pure U and Fe, Fe–15 wt.%Cr or Fe–15 wt.%Cr–15 wt.%Ni alloy, and annealed at high temperature ranging from 580 to 700 °C. The microstructures and concentration profiles that developed from the diffusion anneal were examined by scanning electron microscopy, and X-ray energy dispersive spectroscopy (XEDS), respectively. Thick U6Fe and thin UFe2 phases were observed to develop with solubilities: up to 2.5 at.% Ni in U6(Fe,Ni), up to 20 at.%Cr in U(Fe, Cr)2, and up to 7 at.%Cr and 14 at.% Ni in U(Fe, Cr, Ni)2. The interdiffusion and reactions in the U vs. Fe and U vs. Fe–Cr–Ni exhibited a similar temperature dependence, while the U vs. Fe–Cr diffusion couples, without the presence of Ni, yielded greater activation energy for the growth of intermetallic phases – lower growth rate at lower temperature but higher growth rate at higher temperature. |
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"Fuel-Matrix Chemical Interaction Between U-7wt.%Mo Alloy and Mg"
Ke Huang, Dennis Keiser, Yongho Sohn, H. Heinrich,
Defects and Diffusion Forum
Vol. 333
2013
199-206
Link
A solid-to-solid, U-7wt.%Mo vs. Mg diffusion couple was assembled and annealed at 550°C for 96 hours. Themicrostructurein the interdiffusion zone and the development of concentration profiles were examined via scanning electron microscopy, transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy. A TEM specimen was prepared at the interface between U-7wt.%Mo andMgusing focused ion beam in-situ lift-out. The U-7wt.%Mo alloy was bonded well tothe Mg at the atomic scale, without any evidence of oxidation, cracks or pores.Despite the good bonding, very little or negligible interdiffusion was observed.This is consistent with the expectation based on negligible solubilities according to the equilibrium phase diagrams. Along with other desirableproperties, Mgis a potential inert matrix or barrier materialfor U-Mo fuel alloy systembeing developed forthe Reduced Enrichment for Research and Test Reactor (RERTR) program. |
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"Growth Kinetics and Microstructural Evolution during Hot Isostatic Pressing of U-10wt.%Mo Monolithic Fuel Plate in AA6061 Cladding with Zr Diffusion Barrier"
Young Joo Park, Ke Huang, Dennis Keiser, Jan-Fong Jue, Barry Rabin, G. Moore, Yongho Sohn,
Journal of Nuclear Materials
Vol. 447
2014
215-224
Link
Phase constituents and microstructure changes in RERTR fuel plate assemblies as functions of temperature and duration of hot-isostatic pressing (HIP) during fabrication were examined. The HIP process was carried out as functions of temperature (520, 540, 560 and 580 °C for 90 min) and time (45–345 min at 560 °C) to bond 6061 Al-alloy to the Zr diffusion barrier that had been co-rolled with U-10 wt.% Mo (U10Mo) fuel monolith prior to the HIP process. Scanning and transmission electron microscopies were employed to examine the phase constituents, microstructure and layer thickness of interaction products from interdiffusion. At the interface between the U10Mo and Zr, following the co-rolling, the UZr2 phase was observed to develop adjacent to Zr, and the α-U phase was found between the UZr2 and U10Mo, while the Mo2Zr was found as precipitates mostly within the α-U phase. The phase constituents and thickness of the interaction layer at the U10Mo-Zr interface remained unchanged regardless of HIP processing variation. Observable growth due to HIP was only observed for the (Al,Si)3Zr phase found at the Zr/AA6061 interface, however, with a large activation energy of 457 ± 28 kJ/mole. Thus, HIP can be carried to improve the adhesion quality of fuel plate without concern for the excessive growth of the interaction layer, particularly at the U10Mo-Zr interface with the α-U, Mo2Zr, and UZr2 phases.
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"Interdiffusion and Reaction Between Uranium and Iron"
Ke Huang, Young Joo Park, Ashley Ewh, Bulent Sencer, Rory Kennedy, Kevin Coffey, Yongho Sohn,
Journal of Nuclear Materials
Vol. 424
2012
82-88
Link
Metallic uranium alloy fuels cladded in stainless steel are being examined for fast reactors that operate at high temperature. In this work, solid-to-solid diffusion couples were assembled between pure U and Fe, and annealed at 853 K, 888 K and 923 K where U exists as orthorhombic α, and at 953 K and 973 K where U exists as tetragonal β. The microstructures and concentration profiles developed during annealing were examined by scanning electron microscopy and electron probe microanalysis, respectively. U6Fe and UFe2 intermetallics developed in all diffusion couples, and U6Fe was observed to grow faster than UFe2. The interdiffusion fluxes of U and Fe were calculated to determine the integrated interdiffusion coefficients in U6Fe and UFe2. The extrinsic (KI) and intrinsic growth constants (KII) of U6Fe and UFe2 were also calculated according to Wagner’s formalism. The difference between KI and KII of UFe2 indicate that its growth was impeded by the fast-growing U6Fe phase. However, the thin UFe2 played only a small role on the growth of U6Fe as its KI and KII values were determined to be similar. The allotropic transformation of uranium (orthorhombic α to tetragonal β phase) was observed to influence the growth of U6Fe directly, because the growth rate of U6Fe changed based on variation of activation energy. The change in chemical potential and crystal structure of U due to the allotropic transformation affected the interdiffusion between U and U6Fe. Faster growth of U6Fe is also examined with respect to various factors including crystal structure, phase diagram, and diffusion.
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"Interdiffusion between Potential Diffusion Barrier Mo and U-Mo Metallic Fuel Alloy for RERTR Applications"
Ke Huang, Young Joo Park, Dennis Keiser, Yongho Sohn,
Journal of Phase Equilibria and Diffusion
Vol. 34
2013
307-312
Link
U-Mo alloys are being developed as low enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor Program. Previous investigation has shown that the interdiffusion between U and Mo in γ(bcc)-U solid solution is very slow. This investigation explored interdiffusional behavior, especially in regions with high Mo concentration, and the potential application of Mo as a barrier material to reduce the interaction between U-Mo fuel and Al alloys matrix. Solid-to-solid U-10wt.%Mo versus Mo diffusion couples were assembled and annealed at 600, 700, 800, 900 and 1000 °C for 960, 720, 480, 240, 96 h, respectively. The interdiffusion microstructures and concentration profiles were examined via scanning electron microscopy and electron probe microanalysis, respectively. As the Mo concentration increased from 22 to 32 at.%, the interdiffusion coefficient decreased while the activation energy increased. The growth rate constant of the interdiffusion zone between U-10wt.%Mo versus Mo was also determined and compared to be 104-105 times lower than those of U-10wt.%Mo versus Al and U-10wt.%Mo versus Al-Si systems. Other desirable physical properties of Mo as a barrier material, such as neutron adsorption rate, melting point and thermal conductivity, are also highlighted. |
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"Interdiffusion Between Zr Diffusion Barrier and U-Mo Alloy"
Ke Huang, Young Joo Park, Dennis Keiser, Yongho Sohn,
Journal of Phase Equilibria and Diffusion
Vol. 33
2012
443-449
Link
U-Mo alloys are being developed as low-enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) program. Significant reactions have been observed between U-Mo fuels and Al or Al alloy matrix. Refractory metal Zr has been proposed as barrier material to reduce the interactions. In order to investigate the compatibility and barrier effects between U-Mo alloy and Zr, solid-to-solid U-10wt.%Mo versus Zr diffusion couples were assembled and annealed at 600, 700, 800, 900, and 1000 °C for various times. The microstructures and concentration profiles due to interdiffusion and reactions were examined via scanning electron microscopy and electron probe microanalysis, respectively. Intermetallic phase Mo2Zr was found at the interface, and its population increased when annealing temperature decreased. Diffusion paths were also plotted on the U-Mo-Zr ternary phase diagrams with good consistency. The growth rate of interdiffusion zone between U-10wt.%Mo and Zr was also calculated under the assumption of parabolic diffusion and was determined to be about 103 times lower than the growth rate of diffusional interaction layer found in diffusion couples U-10wt.%Mo versus Al or Al-Si alloy. Other desirable physical properties of Zr as barrier material, such as neutron adsorption rate, melting point, and thermal conductivity, are presented as supplementary information to demonstrate the great potential of Zr as the diffusion barrier for U-Mo fuel systems in RERTR. |
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"Interdiffusion, Intrinsic Diffusion, Atomic Mobility, and Vacancy Wind Effects in γ(bcc) Uranium-Molybdenum Alloy"
Ke Huang, Dennis Keiser, Yongho Sohn,
Metallurgical and Materials Transactions A
Vol. 44
2012
738-746
Link
U-Mo alloys are being developed as low enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) Program. In order to understand the fundamental diffusion behavior of this system, solid-to-solid pure U vs Mo diffusion couples were assembled and annealed at 923 K, 973 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 800 °C, 900 °C, and 1000 °C) for various times. The interdiffusion microstructures and concentration profiles were examined via scanning electron microscopy and electron probe microanalysis, respectively. As the Mo concentration increased from 2 to 26 at. pct, the interdiffusion coefficient decreased, while the activation energy increased. A Kirkendall marker plane was clearly identified in each diffusion couple and utilized to determine intrinsic diffusion coefficients. Uranium intrinsically diffused 5-10 times faster than Mo. Molar excess Gibbs free energy of U-Mo alloy was applied to calculate the thermodynamic factor using ideal, regular, and subregular solution models. Based on the intrinsic diffusion coefficients and thermodynamic factors, Manning’s formalism was used to calculate the tracer diffusion coefficients, atomic mobilities, and vacancy wind parameters of U and Mo at the marker composition. The tracer diffusion coefficients and atomic mobilities of U were about five times larger than those of Mo, and the vacancy wind effect increased the intrinsic flux of U by approximately 30 pct. |
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"Microstructural Analysis of As-Processed U-10wt.%Mo Monolithic Fuel Plate in AA6061 Matrix with Zr Diffusion Barrier"
Emmanuel Perez, B. Yao, Dennis Keiser, Yongho Sohn,
Journal of Nuclear Materials
Vol. 402
2010
8-14
Link
For higher U-loading in low-enriched U–10 wt.%Mo fuels, monolithic fuel plate clad in AA6061 is being developed as a part of Reduced Enrichment for Research and Test Reactor (RERTR) program. This paper reports the first characterization results from a monolithic U–10 wt.%Mo fuel plate with a Zr diffusion barrier that was fabricated as part of a plate fabrication campaign for irradiation testing in the Advanced Test Reactor (ATR). Both scanning and transmission electron microscopy (SEM and TEM) were employed for analysis. At the interface between the Zr barrier and U–10 wt.%Mo, going from Zr to U(Mo), UZr2, γ-UZr, Zr solid-solution and Mo2Zr phases were observed. The interface between AA6061 cladding and Zr barrier plate consisted of four layers, going from Al to Zr, (Al, Si)2Zr, (Al, Si)Zr3 (Al, Si)3Zr, and AlSi4Zr5. Irradiation behavior of these intermetallic phases is discussed based on their constituents. Characterization of as-fabricated phase constituents and microstructure would help understand the irradiation behavior of these fuel plates, interpret post-irradiation examination, and optimize the processing parameters of monolithic fuel system. |
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"Microstructural Characterization of U-7Mo/Al-Si Alloy Matrix Dispersion Fuel Plates Fabricated at 500 C"
Emmanuel Perez, Dennis Keiser, Jan-Fong Jue, Bo Yao, Yongho Sohn, Curtis Clark,
Journal of Nuclear Materials
Vol. 412
2011
90-99
Link
The starting microstructure of a dispersion fuel plate will impact the overall performance of the plate during irradiation. To improve the understanding of the as-fabricated microstructures of U–Mo dispersion fuel plates, particularly the interaction layers that can form between the fuel particles and the matrix, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses have been performed on samples from depleted U–7Mo (U–7Mo) dispersion fuel plates with either Al–2 wt.% Si(Al–2Si) or AA4043 alloy matrix. It was observed that in the thick interaction layers, U(Al, Si)3 and U6Mo4Al43 were present, and in the thin interaction layers, (U, Mo) (Al, Si)3, U(Al, Si)4, U3Si3Al2, U3Si5, and possibly USi-type phases were observed. The U3Si3Al2 phase contained some Mo. Based on the results of this investigation, the time that a dispersion fuel plate is exposed to a relatively high temperature during fabrication will impact the nature of the interaction layers around the fuel particles. Uniformly thin, Si-rich layers will develop around the U–7Mo particles for shorter exposure times, and thicker, Si-depleted layers will develop for the longer exposure times. |
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"Microstructural Characterization of U-Nb-Zr, U-Mo-Nb, and U-Mo-Ti Alloys via Electron Microscopy"
Emmanuel Perez, Ashley Ewh, Dennis Keiser, Yongho Sohn,
Journal of Phase Equilibria and Diffusion
Vol. 31
2010
216-222
Link
Ternary uranium molybdenum alloys are being examined for use as dispersion and monolithic nuclear fuels in research and test reactors. In this study, three such ternary alloys, with compositions U-10Nb-4Zr, U-8Mo-3Nb, and U-7Mo-3Ti in wt.%, were examined using scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) with high angle annular dark field (HAADF) imaging via scanning transmission electron microscopy (STEM). These alloys were homogenized at 950 °C for 96 h and were expected to be single-phase bcc-γ-U. However, upon examination, it was determined that despite homogenization, each of the alloys contained a small volume fraction precipitate phase. Through SEM and XRD, it was confirmed that the matrix retained the bcc-γ-U phase. TEM specimens were prepared using site-specific focused ion beam (FIB) in situ lift out (INLO) technique to include at least one precipitate from each alloy. By electron diffraction, the precipitate phases for the U-10Nb-4Zr, U-8Mo-3Nb, and U-7Mo-3Ti alloys were identified as bcc-(Nb,Zr), bcc-(Mo,Nb), and bcc-(Mo,Ti) solid solutions, respectively. The composition and phase information collected in this study was then used to construct ternary isotherms for each of these alloys at 950 °C. |
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"Microstructural development from interdiffusion and reaction between U-Mo and AA6061 alloys annealed at 600° and 550 °C"
Dennis Keiser, Emmanuel Perez, Yongho Sohn,
Journal of Nuclear Materials
Vol. 477
2016
178-192
Link
The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the UMo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, U7 wt%Mo, U10 wt%Mo, and U12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanning electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples UMo vs. high purity Al and binary AlSi alloys. The diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061. |
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"Microstructure characterization of as-fabricated and 475ºC annealed U-7wt.%Mo dispersion fuel in Al-Si alloy matrix"
Emmanuel Perez, Bo Yao, Dennis Keiser, Jan-Fong Jue, Curtis Clark, Nicolas Woolstenhulme, Yongho Sohn,
Journal of Alloys and Compounds
Vol. 509
2011
9487-9496
Link
High-density uranium (U) alloys with an increased concentration of U are being examined for the development of research and test reactors with low enriched metallic fuels. The U–Mo fuel alloy dispersed in Al–Si alloy has attracted particular interest for this application. This paper reports our detailed characterization results of as-fabricated and annealed (475 °C for 4 h) U–Mo dispersion fuels in Al–Si matrix with a Si concentration of 2 and 5 wt.%, named as “As2Si”, “As5Si”, “An2Si”, “An5Si” accordingly. Techniques employed for the characterization include scanning electron microscopy and transmission electron microscopy with specimen prepared by focused ion beam in situ lift-out. Fuel plates with Al–5 wt.% Si matrix consistently yielded thicker interaction layers developed between U–Mo particles and Al–Si matrix, than those with Al–2 wt.% Si matrix, given the same processing parameters. A single layer of interaction zone was observed in as-fabricated samples (i.e., “As2Si”, “As5Si”), and this layer mainly consisted of U3Si3Al2 phase. The annealed samples contained a two-layered interaction zone, with a Si-rich layer near the U–Mo side, and an Al-rich layer near the Al–Si matrix side. The U3Si5 appeared as the main phase in the Si-rich layer in “An2Si” sample, while both U3Si5 and U3Si3Al2 were identified in sample “An5Si”. The Al-rich layer in sample “An2Si” was amorphous, whereas that in sample “An5Si” mostly consisted of crystalline U(Al,Si)3, along with a small fraction of U(Al,Si)4 and U6Mo4Al43 phases. The influence of Si on the diffusion and reaction in the development of interaction layers in U(Mo)/Al(Si) is discussed in the light of growth-controlling mechanisms and irradiation performance. |
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"Phase Constituents and Microstructure of Interaction Layer Formed in U-Mo Alloys vs Al Diffusion Couples Annealed at 873 K (600 °C)"
Emmanuel Perez, Dennis Keiser, Yongho Sohn,
Metallurgical and Materials Transactions A
Vol. 42
2011
3071-3083
Link
U-Mo dispersion and monolithic fuels are being developed to fulfill the requirements for research reactors, under the Reduced Enrichment for Research and Test Reactors program. In dispersion fuels, particles of U-Mo alloys are embedded in the Al-alloy matrix, while in monolithic fuels, U-Mo monoliths are roll bonded to the Al-alloy matrix. In this study, interdiffusion and microstructural development in the solid-to-solid diffusion couples, namely, U-15.7 at. pct Mo (7 wt pct Mo) vs pure Al, U-21.6 at. pct Mo (10 wt pct Mo) vs pure Al, and U-25.3 at. pct Mo (12 wt pct Mo) vs pure Al, annealed at 873 K (600 °C) for 24 hours, were examined in detail. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA) were employed to examine the development of a very fine multiphase interaction layer with an approximately constant average composition of 80 at. pct Al. Extensive TEM was carried out to identify the constituent phases across the interaction layer based on selected area electron diffraction and convergent beam electron diffraction (CBED). The cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43, and cubic-UMo2Al20 phases were identified within the interaction layer that included two- and three-phase layers. Residual stress from large differences in molar volume, evidenced by vertical cracks within the interaction layer, high Al mobility, Mo supersaturation, and partitioning toward equilibrium in the interdiffusion zone were employed to describe the complex microstructure and phase constituents observed. A mechanism by compositional modification of the Al alloy is explored to mitigate the development of the U6Mo4Al43 phase, which exhibits poor irradiation behavior that includes void formation and swelling. |
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"Phase constituents of Al-rich U–Mo–Al alloys examined by transmission electron microscopy"
Emmanuel Perez, Ashley Ewh, Jinwei Liu, Dennis Keiser, Yongho Sohn,
Journal of Nuclear Materials
Vol. 394
2009
160-165
Link
To supplement the understanding of diffusional interactions involving Al-rich region of the U–Mo–Al system, alloys with composition 85.7Al–11.44U–2.86Mo and 87.5Al–10U–2.5Mo in at.%, were examined to determine the equilibrium phase constituents at 500 °C. These alloys were triple arc-melted, homogenized at 500 °C for 200 h, and water-quenched to preserve the high temperature microstructure. X-ray diffraction, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (XEDS), and transmission electron microscopy (TEM) with high angle annular dark field (HAADF) imaging via scanning transmission electron microscopy (STEM) were employed for the characterization. Alloy specimens for TEM/STEM were prepared using site-specific focused ion beam (FIB) in situ lift-out (INLO) technique. Despite the homogenization time and temperature, five different phases, namely fcc-Al solid solution, cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43 and diamond cubic-UMo2Al20, were observed. Based on U–Al, U–Mo and Al–Mo binary phase diagrams, previously proposed U–Mo–Al isotherms, and the solidification microstructure of these alloys, the Al-rich region of the equilibrium ternary isotherm at 500 °C was constructed. The fcc-Al solid solution, orthorhombic-UAl4, and diamond cubic-UMo2Al20 which were determined to be the equilibrium phases in 85.7Al–11.44U–2.86Mo and 87.5Al–10U–2.5Mo alloys. |
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"Phase decomposition of ?-U (bcc) in U-10 wt% Mo fuel alloy during hot isostatic pressing of monolithic fuel plat"
Nicholas Eriksson, Dennis Keiser, Ryan Newell, Young Joo Park, Yongho Sohn,
Journal of Nuclear Materials
Vol. 480
2016
271-280
Link
Eutectoid decomposition of γ-phase (cI2) into α-phase (oC4) and γ′-phase (tI6) during the hot isostatic pressing (HIP) of the U-10 wt% Mo (U10Mo) alloy was investigated using monolithic fuel plate samples consisting of U10Mo fuel alloy, Zr diffusion barrier and AA6061 cladding. The decomposition of the γ-phase was observed because the HIP process is carried out near the eutectoid temperature, 555 °C. Initially, a cellular structure, consisting of γ′-phase surrounded by α-phase, developed from the destabilization of the γ-phase. The cellular structure further developed into an alternating lamellar structure of α- and γ′-phases. Using scanning electron microscopy and transmission electron microscopy, qualitative and quantitative microstructural analyses were carried out to identify the phase constituents, and elucidate the microstructural development based on time-temperature-transformation diagram of the U10Mo alloy. The destabilization of γ -phase into α- and γ′-phases would be minimized when HIP process was carried out with rapid ramping/cooling rate and dwell temperature higher than 560 °C. |
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"Phase development in a U–7 wt.% Mo vs. Al–7 wt.% Ge diffusion couple"
Emmanuel Perez, Dennis Keiser, Yongho Sohn,
Journal of Nuclear Materials
Vol. 441
2013
159-167
Link
Fuel development for the Reduced Enrichment for Research and Test Reactors (RERTR) program has demonstrated that U–Mo alloys in contact with Al develop interaction regions with phases that have poor irradiation behavior. The addition of Si to the Al has been considered with positive results. In this study, compositional modification is considered by replacing Si with Ge to determine the effect on the phase development in the system. The microstructural and phase development of a diffusion couple of U–7 wt.% Mo in contact with Al–7 wt.% Ge was examined by transmission electron microscopy, scanning electron microscopy and energy dispersive spectroscopy. The interdiffusion zone developed a microstructure that included the cubic-UGe3 phase and amorphous phases. The UGe3 phase was observed with and without Mo and Al solid solution developing a (U,Mo)(Al,Ge)3 phase. |
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"Radiation effects on interface reactions of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni)"
Bulent Sencer, Lin Shao, Yongho Sohn, Di Chen, Chaochen Wei, Michael Martin, Xuemei Wang, Young Joo Park, Ed Dein, Kevin Coffey, Rory Kennedy,
Journal of Nuclear Materials
Vol. 456
2015
302-310
Link
We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 °C or 550 °C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules. |
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"Role of Si on Diffusional Interaction between U-Mo and Al-Si Alloys at 823K (550 C)"
Emmanuel Perez, Dennis Keiser, Yongho Sohn,
Metallurgical and Materials Transactions A
Vol. 44
2012
584-595
Link
U-Mo dispersions in Al-alloy matrix and monolithic fuels encased in Al-alloy are under development to fulfill the requirements for research and test reactors to use low-enriched molybdenum stabilized uranium alloys fuels. Significant interaction takes place between the U-Mo fuel and Al during manufacturing and in-reactor irradiation. The interactions products are Al-rich phases with physical and thermal characteristics that adversely affect fuel performance and lead to premature failure. Detailed analysis of the interdiffusion and microstructural development of this system was carried through diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo in contact with pure Al, Al-2wt.%Si, and Al-5wt.%Si, annealed at 823K for 1, 5 and 20 hours. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed for the analysis. Diffusion couples consisting of U-Mo vs. pure Al contained UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases. The addition of Si to the Al significantly reduced the thickness of the interdiffusion zone. The interdiffusion zones developed Al and Si enriched regions, whose locations and size depended on the Si and Mo concentrations in the terminal alloys. In the couples, the (U,Mo)(Al,Si)3 phase was observed throughout interdiffusion zone, and the U6Mo4Al43 and UMo2Al20 phases were observed only where the Si concentrations were low.
(PDF) Role of Si on the Diffusional Interactions Between U-Mo and Al-Si Alloys at 823 K (550 °C). Available from: https://www.researchgate.net/publication/255813658/download [accessed Sep 06 2018]. |
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"Selected Observations in Phase Constituents, Growth Kinetics and Microstructural Development of Aluminides in U-Mo vs. Al and 6061 Diffusion Couples Annealed at 600°C"
Emmanuel Perez, Dennis Keiser, Yongho Sohn,
Defects and Diffusion Forum
Vol. 289-292
2009
41-49
Link
This paper presents selected experimental observations of phase constituents, growth kinetics, and microstructural development of aluminide phases that develop in solid-to-solid diffusion couples assembled with U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. Al and 6061 alloy after a diffusion anneal at 600°C for 24 hours. Scanning electron microscopy coupled with energy dispersive spectroscopy, electron microprobe analysis, and transmission electron microscopy via focused ion beam in-situ lift-out were employed to characterize the interaction layer that develops by interdiffusion. While concentration profiles exhibited no significant gradients, microstructural analysis revealed the presence of extremely complex and nano-scale phase constituents with presence of orthorhombic--U, cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43 and diamond cubic-UMo2Al20 phases. Presence of multi-phase layers with microstructure, which suggest a significant role of grain boundary diffusion, was observed. |
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"Thermotransport in γ(bcc) U-Zr Alloys: A Phase-Field Model Study"
Rashmi Mohanty, J. Bush, Maria Okuniewski, Yongho Sohn,
Journal of Nuclear Materials
Vol. 414
2011
211-216
Link
Atomic transport in the presence of a temperature gradient, commonly known as thermotransport or the thermomigration phenomenon, was simulated for U–Zr alloys using a phase-field model derived from irreversible thermodynamics. The free energy of the U–Zr system, a necessary ingredient for the phase-field-model, was directly incorporated from the available thermodynamic database. Kinetic parameters such as atomic mobility and heat of transport terms were obtained from experimental values reported in the literature. The model was applied to a single-phase (bcc-γ phase) alloy and to a diffusion couple consisting of two single-phase (bcc-γ phase) alloys of different compositions, both subjected to a constant temperature gradient. Constituent redistribution in the absence and presence of a compositional gradient was examined. An enrichment of Zr with a corresponding depletion of U was observed at the hot end of the initially homogeneous single-phase alloy. A similar atomic transport behavior was observed in the diffusion couple, where the magnitude and direction of the final composition gradient was dictated by the combined influence of atomic mobility and heat of transport terms. |
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"Understanding the Phase Equilibrium and Irradiation Effects in Fe-Zr Diffusion Couples"
Assel Aitkaliyeva, Bulent Sencer, Lin Shao, Yongho Sohn, Chao-Chen Wei, Zhiping Luo, Ashley Ewh, Rory Kennedy, Michael Myers, Joseph Wallace, M. J. General, Michael Martin,
Journal of Nuclear Materials
Vol. 432
2013
205-211
Link
We have studied the radiation effects in Fe–Zr diffusion couples, formed by thermal annealing of a mechanically bonded binary system at 850 °C for 15 days. After irradiation with 3.5 MeV Fe ions at 600 °C, a cross sectional specimen was prepared by using a focused-ion-beam-based lift out technique and was characterized using scanning/transmission electron microscopy, selected-area diffraction and X-ray energy dispersive spectroscopy analyses. Comparison studies were performed in localized regions within and beyond the ion projected range and the following observations were obtained: (1) the interaction layer consists of FeZr3, FeZr2, Fe2Zr, and Fe23Zr6; (2) large Fe23Zr6 particles with smaller core particles of Zr-rich Fe2Zr are found within the a-Fe matrix; (3) Zr diffusion is significantly enhanced in the ion bombarded region, leading to the formation of an Fe–Zr compound; (4) grains located within the interaction layer are much smaller in the ion bombarded region and are associated with new crystal growth and nanocrystal formation; and (5) large a-Fe particles form on the surface of the Fe side, but the particles are limited to the region close to the interaction layer. These studies reveal the complexity of the interaction phase formation in an Fe–Zr binary system and the accelerated microstructural changes under irradiation. |
"Diffision Couple Expereiments: Opportunities and Challenges in Determining Thermo-Kinetic and Functional Properties" Yongho Sohn, 13th International Conference on Diffusion in Solids and Liquids June 26-30, (2017) | |
"Interdiffusion, Reactions and Phase Transformations Observed during Fabrication of Low Enriched Metallic Fuel System for Research and Test Reactors" Nicholas Eriksson, Dennis Keiser, Ryan Newell, Young Joo Park, Yongho Sohn, 10th International Conference on Diffusion in Materials (DIMAT-2017) May 7-12, (2017) |
"Strength and ductility enhancement by Mo addition to an Al-Ce alloy designed for additive manufacturing" Thinh Huynh, Ashton Grace, Le Zhou, Marko Knezevic, Tanner Olson, Amberlee Haselhuhn, Yongho Sohn, Kevin Graydon, [2025] Materials Science and Engineering: A · DOI: 10.1016/j.msea.2025.149004 | |
"Microstructure and Mechanical Characterization of AISI 4340 Steel Additively Manufactured by Laser Powder Bed Fusion"
Thinh Huynh, Nemanja Kljestan, Marko Knezevic, Yongho Sohn, Felix Aguilar,
[2025]
Metals
· DOI: 10.3390/met15040412
The effects of laser powder bed fusion (LPBF) parameters, such as power (200 to 350 W) and scan speeds (from 200 to 2000 mm/s), on the microstructure and mechanical properties of high-strength, low-alloy (HSLA) AISI 4340 steel were examined. A wide range of volumetric energy density (VED) between 93 and 162 J/mm3 produced samples with relative densities greater than 99.8%. The optimal parameter set was identified with laser power = 200 W, scan speed = 600 mm/s, hatch spacing = 0.12 mm, and slice thickness = 0.03, corresponding to VED = 92.6 J/mm3. Scanning electron microscopy revealed a predominantly martensitic microstructure for all processing parameters examined, although X-ray diffraction revealed the minor presence of retained austenite within the as-fabricated 4340 steel. Using the optimized LPBF parameters, the as-fabricated 4340 steel exhibited a yield strength of 1317 MPa ± 16 MPa, ultimate tensile strength of 1538 MPa ± 22 MPa, and 18.6 ± 1% strain at failure. These are similar to wrought 4340 steel quenched and tempered between 400 and 600 °C. |
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"Parameter Optimization and Flaw Type Dependent Tensile Properties of 15‐5PH Stainless Steel Manufactured by Laser Powder Bed Fusion"
Cameron Lucas, Asif Mahmud, Nemanja Kljestan, Marko Knezevic, Yongho Sohn, Nicolas Ayers,
[2024]
Advanced Engineering Materials
· DOI: 10.1002/adem.202401346
Careful consideration of processing parameters to mitigate defect formation is crucial to ensure reliability of components produced by laser powder bed fusion (LPBF). In this work, additive manufacturing parameter optimization and flaw type dependent tensile properties of 15‐5 precipitation hardened (PH) stainless steel produced by LPBF is examined to understand the correlation among processing parameters, flaw types, and corresponding tensile mechanical behavior. It is reported that LPBF samples with keyhole (KH) pores exhibit superior mechanical properties compared to those induced with lack‐of‐fusion (LOF) flaws, for a given relative density level. Diminished mechanical properties in samples with LOF flaws is correlated to the flaws’ irregular shapes and sharp corners, causing stress concentration. Minimal improvements to the mechanical properties of LOF‐induced samples, despite increasing relative density, indicate even small amounts of LOF flaws cause stress concentration and crack initiation. Conversely, KH pores exhibit high circularity and lower curvature values, and samples with KH pores demonstrate a strong correlation between tensile properties and relative density. Findings from this study suggest that when suboptimal LPBF processing is inevitable, favoring excessive energy input to induce KH pores over LOF flaws can lead to more predictable mechanical behavior of LPBF components. |
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"Additive manufacturing of Al18Co30Cr10Fe10Ni32 high entropy alloy by gas atomization and laser powder bed fusion" Thinh Huynh, Nemanja Kljestan, Kevin Graydon, Asif Mahmud, Marko Knezevic, Brandon McWilliams, Kyu Cho, Yongho Sohn, Abhishek Mehta, [2023] Materials Letters · DOI: 10.1016/j.matlet.2023.134942 | |
"Tensile behavior of diffusion bonded AA6061 - AA6061 with variation in cooling method" Jeongmin Woo, Jeffrey J. Giglio, Jan-Fong Jue, Dennis D. Keiser, James I. Cole, Yongho Sohn, Abhishek Mehta, [2023] Materials Science and Engineering: A · DOI: 10.1016/j.msea.2023.145459 | |
"Synergy of tensile strength and high cycle fatigue properties in a novel additively manufactured Al-Ni-Ti-Zr alloy with a heterogeneous microstructure" Priyanka Agrawal, Saket Thapliyal, Priyanshi Agrawal, Abhijeet Dhal, Shivakant Shukla, Le Zhou, Yongho Sohn, Rajiv S. Mishra, Ravi Sankar Haridas, [2023] Additive Manufacturing · DOI: 10.1016/j.addma.2022.103380 | |
"Flaw type dependent tensile properties of 316L stainless steel additively manufactured by laser powder bed fusion" Nemanja Kljestan, Nicolas Ayers, Marko Knezevic, Yongho Sohn, Nathalia Diaz Vallejo, [2022] Results in Materials · DOI: 10.1016/j.rinma.2022.100315 | |
"Microstructural characteristics and mechanical properties of additively manufactured Cu–10Sn alloys by laser powder bed fusion" Le Zhou, Holden Hyer, Thinh Huynh, Binghao Lu, Kevin Graydon, Erica J. Drobner, Sun Hong Park, Yongho Sohn, Abhishek Mehta, [2022] Materials Science and Engineering: A · DOI: 10.1016/j.msea.2022.142775 | |
"Microstructure, mechanical performance, and corrosion behavior of additively manufactured aluminum alloy 5083 with 0.7 and 1.0 wt% Zr addition" Holden Hyer, Jinfa Chang, Abhishek Mehta, Thinh Huynh, Yang Yang, Yongho Sohn, Le Zhou, [2021] Materials Science and Engineering: A · DOI: 10.1016/j.msea.2021.141679 | |
"Investigation of sluggish diffusion in FCC Al0.25CoCrFeNi high-entropy alloy" Yongho Sohn, Abhishek Mehta, [2021] Materials Research Letters · DOI: 10.1080/21663831.2021.1878475 | |
"Composition-dependent solidification cracking of aluminum-silicon alloys during laser powder bed fusion" Le Zhou, Abhishek Mehta, Sharon Park, Thinh Huynh, Shutao Song, Yuanli Bai, Kyu Cho, Brandon McWilliams, Yongho Sohn, Holden Hyer, [2021] Acta Materialia · DOI: 10.1016/j.actamat.2021.116698 | |
"Fundamental Core Effects in Transition Metal High-Entropy Alloys: “High-Entropy” and “Sluggish Diffusion” Effects"
Yong Ho Sohn, Abhishek Mehta,
[2021]
Diffusion Foundations
· DOI: 10.4028/www.scientific.net/df.29.75
High entropy alloys (HEAs) are equimolar multi-principal-element alloys (MPEAs) that are different from traditional solvent-based multicomponent alloys based on the concept of alloy design. Based on initial work by Yeh and co-workers, HEAs were postulated to exhibit four “ |
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"Laser powder bed fusion of Al–10 wt% Ce alloys: microstructure and tensile property" Thinh Huynh, Sharon Park, Holden Hyer, Abhishek Mehta, Shutao Song, Yuanli Bai, Brandon McWilliams, Kyu Cho, Yongho Sohn, Le Zhou, [2020] Journal of Materials Science · DOI: 10.1007/s10853-020-05037-z | |
"Anomalous growth of Al8Mo3 phase during interdiffusion and reaction between Al and Mo" Le Zhou, Dennis D. Keiser, Yongho Sohn, Abhishek Mehta, [2020] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2020.152337 · ISSN: 0022-3115 | |
"Understanding the Laser Powder Bed Fusion of AlSi10Mg Alloy" Le Zhou, Sharon Park, Guilherme Gottsfritz, George Benson, Bjorn Tolentino, Brandon McWilliams, Kyu Cho, Yongho Sohn, Holden Hyer, [2020] Metallography, Microstructure, and Analysis · DOI: 10.1007/s13632-020-00659-w · ISSN: 2192-9262 | |
"Interdiffusion, Solubility Limit, and Role of Entropy in FCC Al-Co-Cr-Fe-Ni Alloys" Yongho Sohn, Abhishek Mehta, [2020] Metallurgical and Materials Transactions A · DOI: 10.1007/s11661-020-05742-z · ISSN: 1073-5623 | |
"Process-Dependent Composition, Microstructure, and Printability of Al-Zn-Mg and Al-Zn-Mg-Sc-Zr Alloys Manufactured by Laser Powder Bed Fusion" Holden Hyer, Saket Thapliyal, Rajiv S. Mishra, Brandon McWilliams, Kyu Cho, Yongho Sohn, Le Zhou, [2020] Metallurgical and Materials Transactions A · DOI: 10.1007/s11661-020-05768-3 · ISSN: 1073-5623 | |
"Additive manufacturing of dense WE43 Mg alloy by laser powder bed fusion" Le Zhou, George Benson, Brandon McWilliams, Kyu Cho, Yongho Sohn, Holden Hyer, [2020] Additive Manufacturing · DOI: 10.1016/j.addma.2020.101123 · ISSN: 2214-8604 | |
"Spark Plasma Sintered B4C—Structural, Thermal, Electrical and Mechanical Properties"
Nina Orlovskaya, Holden Hyer, Yongho Sohn, Mykola Lugovy, DongGi Ha, Miladin Radovic, Elinor G. Castle, Michael John Reece, Pradeep Vallachira Warriam Sasikumar, Laura Conti, Thomas Graule, Jakob Kuebler, Gurdial Blugan, Ruslan Kuliiev,
[2020]
Materials
· DOI: 10.3390/ma13071612
· ISSN: 1996-1944
The structural, thermal, electrical and mechanical properties of fully dense B4C ceramics, sintered using Spark Plasma Sintering (SPS), were studied and compared to the properties of B4C ceramics previously published in the literature. New results on B4C’s mechanical responses were obtained by nanoindentation and ring-on-ring biaxial strength testing. The findings contribute to a more complete knowledge of the properties of B4C ceramics, an important material in many industrial applications. |
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"An integrated computational materials engineering-anchored closed-loop method for design of aluminum alloys for additive manufacturing" Mageshwari Komarasamy, Shivakant Shukla, Le Zhou, Holden Hyer, Sharon Park, Yongho Sohn, Rajiv S. Mishra, Saket Thapliyal, [2020] Materialia · DOI: 10.1016/j.mtla.2019.100574 · ISSN: 2589-1529 | |
"Phase reversion kinetics of thermally decomposed (α + γ′) phases to γ-phase in U – 10 wt% Mo alloy" Abhishek Mehta, Dennis D. Keiser, Yongho Sohn, Ryan Newell, [2020] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2019.151983 · ISSN: 0022-3115 | |
"Numerical simulation of high-pressure gas atomization of two-phase flow: Effect of gas pressure on droplet size distribution" Majid Haghshenas, Sharon Park, Le Zhou, Yongho Sohn, Brandon McWilliams, Kyu Cho, Ranganathan Kumar, Kalpana Hanthanan Arachchilage, [2019] Advanced Powder Technology · DOI: 10.1016/j.apt.2019.08.019 · ISSN: 0921-8831 | |
"Structure-property relationship in high strength and lightweight AlSi10Mg microlattices fabricated by selective laser melting" Holden Hyer, Yongho Sohn, Yuanli Bai, Dazhong Wu, Tianyu Yu, [2019] Materials & Design · DOI: 10.1016/j.matdes.2019.108062 · ISSN: 0264-1275 | |
"Microstructural characteristics of plasma sprayed, electroplated, and co-rolled Zr diffusion barriers in hot isostatic pressed low enriched U-10 wt% Mo monolithic fuel plates" A. Mehta, Y.J. Park, D.D. Keiser, J.I. Cole, Y.H. Sohn, R. Newell, [2019] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2019.05.056 · ISSN: 0022-3115 | |
"Interdiffusion and Reaction Between Al and Zr in the Temperature Range of 425 to 475 °C" Judith Dickson, Ryan Newell, Dennis D. Keiser, Yongho Sohn, Abhishek Mehta, [2019] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-019-00729-9 · ISSN: 1547-7037 | |
"Microstructure and mechanical properties of Zr-modified aluminum alloy 5083 manufactured by laser powder bed fusion" Holden Hyer, Sharon Park, Hao Pan, Yuanli Bai, Katherine P. Rice, Yongho Sohn, Le Zhou, [2019] Additive Manufacturing · DOI: 10.1016/j.addma.2019.05.027 · ISSN: 2214-8604 | |
"Microstructure, precipitates and mechanical properties of powder bed fused inconel 718 before and after heat treatment" Abhishek Mehta, Brandon McWilliams, Kyu Cho, Yongho Sohn, Le Zhou, [2019] Journal of Materials Science & Technology · DOI: 10.1016/j.jmst.2018.12.006 · ISSN: 1005-0302 | |
"Effects of Marker Size and Distribution on the Development of Kirkendall Voids, and Coefficients of Interdiffusion and Intrinsic Diffusion" Abhishek Mehta, Sun Hong Park, Yongho Sohn, Esin Schulz, [2019] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-019-00710-6 · ISSN: 1547-7037 | |
"Microstructure and tensile property of a novel AlZnMgScZr alloy additively manufactured by gas atomization and laser powder bed fusion" Hao Pan, Holden Hyer, Sharon Park, Yuanli Bai, Brandon McWilliams, Kyu Cho, Yongho Sohn, Le Zhou, [2019] Scripta Materialia · DOI: 10.1016/j.scriptamat.2018.08.025 · ISSN: 1359-6462 | |
"Phase Transformations and Microstructural Development in the U-10 Wt Pct Mo Alloy with Varying Zr Contents After Heat Treatments Relevant to the Monolithic Fuel Plate Fabrication Process" Nicholas Eriksson, Ryan Newell, Le Zhou, Esin Schulz, William Sprowes, Felipe Betancor, Youngjoo Park, Dennis D. Keiser, Yongho Sohn, Abhishek Mehta, [2019] Metallurgical and Materials Transactions A · DOI: 10.1007/s11661-018-4987-3 · ISSN: 1073-5623 | |
"Simultaneous Measurement of Isotope-Free Tracer Diffusion Coefficients and Interdiffusion Coefficients in the Cu-Ni System" Abhishek Mehta, Irina V. Belova, Graeme E. Murch, Yongho Sohn, Esin A. Schulz, [2018] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-018-0682-8 · ISSN: 1547-7037 | |
"Diffusion and its Application in NiMnGa Alloys"
Yong Ho Sohn, Le Zhou,
[2018]
Diffusion Foundations
· DOI: 10.4028/www.scientific.net/df.19.80
· ISSN: 2296-3642
Heusler NiMnGa alloys are often categorized as ferromagnetic shape memory alloys or magnetocaloric materials, which are important for both practical applications and fundamental research. The NiMnGa alloys undergo a series of diffusion and diffusionless transformation from high temperature to low temperature. Among these transformation, martensitic transformation from austenitic phase to martensitic phase is critical in determining the properties of the alloys. Although martensitic transformation is considered diffusionless, diffusion also has important applications in the research of NiMnGa alloysDiffusion couples along with equilibrium alloys have been used to determine the ternary phase diagrams in NiMnGa alloys. Phase diagrams are important in selecting NiMnGa alloys, in particular two-phase NiMnGa alloys for practical applications. Furthermore, the diffusion couples effectively assist in the determination of compositions that exhibit martensitic transformation temperature near room temperature. Diffusion coefficients have been assessed for NiMnGa alloys. Tracer diffusivity of Ni, Mn and Ga was reported in a wide temperature range and followed Arrhenius behavior. Two different activation energies were obtained, corresponding to B2 and L21 crystal structure, respectively. Interdiffusion coefficients for NiMnGa alloys with B2 crystal structure are measured, which showed that Ni diffuses the fastest, followed by Mn then Ga. The diffusion coefficients provide useful information for fabricating NiMnGa alloys through diffusional process.A combinatorial approach involving diffusion couples and advance characterization has been developed to investigate the mechanical properties, microstructure and crystallography of NiMnGa alloys rapidly and systematically over a large compositional range. The composition-dependent modulus and hardness for NiMnGa alloys was extracted from the diffusion couples with the help of nanoindentation. Martensitic phases with non-modulated and various modulated crystal structures, and austenitic phase were identified in the interdiffusion zones by transmission electron microscopy. The results demonstrate the capability of using diffusion couples to speed up the discovery of new NiMnGa alloys or other similar alloys showing martensitic transformation. |
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"Direct-Contact Cytotoxicity Evaluation of CoCrFeNi-Based Multi-Principal Element Alloys"
Zi Wang, Isabel Arias, Abhishek Mehta, Yongho Sohn, Stephen Florczyk, Ryan Newell,
[2018]
Journal of Functional Biomaterials
· DOI: 10.3390/jfb9040059
· ISSN: 2079-4983
Transition metal multi-principal element alloys (MPEAs) are novel alloys that may offer enhanced surface and mechanical properties compared with commercial metallic alloys. However, their biocompatibility has not been investigated. In this study, three CoCrFeNi-based MPEAs were fabricated, and the in vitro cytotoxicity was evaluated in direct contact with fibroblasts for 168 h. The cell viability and cell number were assessed at 24, 96, and 168 h using LIVE/DEAD assay and alamarBlue assay, respectively. All MPEA sample wells had a high percentage of viable cells at each time point. The two quaternary MPEAs demonstrated a similar cell response to stainless steel control with the alamarBlue assay, while the quinary MPEA with Mn had a lower cell number after 168 h. Fibroblasts cultured with the MPEA samples demonstrated a consistent elongated morphology, while those cultured with the Ni control samples demonstrated changes in cell morphology after 24 h. No significant surface corrosion was observed on the MPEAs or stainless steel samples following the cell culture, while the Ni control samples had extensive corrosion. The cell growth and viability results demonstrate the cytocompatibility of the MPEAs. The biocompatibility of MPEAs should be investigated further to determine if MPEAs may be utilized in orthopedic implants and other biomedical applications. |
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"Microstructure, precipitates and hardness of selectively laser melted AlSi10Mg alloy before and after heat treatment" Abhishek Mehta, Esin Schulz, Brandon McWilliams, Kyu Cho, Yongho Sohn, Le Zhou, [2018] Materials Characterization · DOI: 10.1016/j.matchar.2018.04.022 · ISSN: 1044-5803 | |
"Effects of Degassing on the Microstructure, Chemistry, and Estimated Mechanical Properties of a Cryomilled Al-Mg Alloy" Le Zhou, Frank Kellogg, Anit Giri, Kyu Cho, Yongho Sohn, Clara Hofmeister, [2018] Metallurgical and Materials Transactions A · DOI: 10.1007/s11661-018-4627-y · ISSN: 1073-5623 | |
"Interdiffusion and reaction between U and Zr" R. Newell, A. Mehta, D.D. Keiser, Y.H. Sohn, Y. Park, [2018] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2018.01.063 · ISSN: 0022-3115 | |
"Microstructural Characterization of AA6061 Versus AA6061 HIP Bonded Cladding–Cladding Interface" Le Zhou, Esin A. Schulz, Dennis D. Keiser, James I. Cole, Yongho Sohn, Abhishek Mehta, [2018] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-018-0629-0 · ISSN: 1547-7037 | |
"Chip Morphology and Chip Formation Mechanisms During Machining of ECAE-Processed Titanium"
David Dabrow, Ryan Newell, Andrew Miller, John K. Schueller, Guoxian Xiao, Steven Y. Liang, Karl T. Hartwig, Nancy J. Ruzycki, Yongho Sohn, Yong Huang, Brian Davis,
[2018]
Journal of Manufacturing Science and Engineering
· DOI: 10.1115/1.4038442
· ISSN: 1087-1357
Severe plastic deformation (SPD) processing such as equal channel angular extrusion (ECAE) has been pioneered to produce ultrafine grained (UFG) metals for improved mechanical and physical properties. However, understanding the machining of SPD-processed metals is still limited. This study aims to investigate the differences in chip morphology when machining ECAE-processed UFG and coarse-grained (CG) titanium (Ti) and understand the chip formation mechanism using metallographic analysis, digital imaging correlation (DIC), and nano-indentation. The chip morphology is classified as aperiodic saw-tooth, continuous, or periodic saw-tooth, and changes with the cutting speed. The chip formation mechanism of the ECAE-processed Ti transitions from cyclic shear localization within the low cutting speed regime (such as 0.1 m/s or higher) to uniform shear localization within the moderately high cutting speed regime (such as from 0.5 to 1.0 m/s) and to cyclic shear localization (1.0 m/s). The shear band spacing increases with the cutting speed and is always lower than that of the CG counterpart. If the shear strain rate distribution contains a shift in the chip flow direction, the chip morphology appears saw-tooth, and cyclic shear localization is the chip formation mechanism. If no such shift occurs, the chip formation is considered continuous, and uniform shear localization is the chip formation mechanism. Hardness measurements show that cyclic shear localization is the chip formation mechanism when localized hardness peaks occur, whereas uniform shear localization is operative when the hardness is relatively constant. |
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"Interdiffusion, Reactions, and Phase Transformations Observed during Fabrication of Low Enriched Uranium Monolithic Fuel System for Research and Test Reactors"
Abhishek Mehta, Young Joo Park, Dennis D. Keiser Jr., Yong Ho Sohn, Ryan Newell,
[2018]
Defect and Diffusion Forum
· DOI: 10.4028/www.scientific.net/ddf.383.10
· ISSN: 1662-9507
Monolithic fuel plates have been developed utilizing low enriched U alloyed with 10 wt.% Mo to replace highly enriched fuels in research and test reactors, in accordance with the goals of the Materials Management and Minimization Reactor Conversion Program. The fuel plates consist of U10Mo fuel, Zr diffusion barrier, and AA6061 cladding. They are fabricated by co-rolling the U10Mo and Zr, which are then encapsulated via hot isostatic pressing of the entire U10Mo/Zr/AA6061 assembly. During fabrication, the metal constituents of the fuel plates undergo phase transformations as well as interdiffusion and reactions at interfaces. The areas of interest are the U10Mo fuel, U10Mo/Zr interface, U10Mo/AA6061 interface, Zr/AA6061 interface, and AA6061-AA6061 bond line. Knowledge of the transformations and growth in the plates is necessary to optimize fabrication parameters and predict behavior as they relate to irradiation performance. Numerous studies have been conducted to analyze these reactions in monolithic fuel plates, and a summary of their observations is provided in this paper. |
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"Composition-dependent interdiffusion coefficient, reduced elastic modulus and hardness in γ-, γ′- and β-phases in the Ni-Al system" Abhishek Mehta, Kyu Cho, Yongho Sohn, Le Zhou, [2017] Journal of Alloys and Compounds · DOI: 10.1016/j.jallcom.2017.07.256 | |
"Tensile properties and microstructure of a cryomilled nanograined Al-Mg alloy near the AA5083 composition" C. Hofmeister, A. Pedigo, A.K. Giri, Y. Sohn, K.C. Cho, M. van den Bergh, B.S. Majumdar, K.H. Kaisar, [2017] Materials Science and Engineering: A · DOI: 10.1016/j.msea.2017.08.073 · ISSN: 0921-5093 | |
"Mechanical anomaly observed in Ni-Mn-Ga alloys by nanoindentation" Anit Giri, Kyu Cho, Yongho Sohn, Le Zhou, [2016] Acta Materialia · DOI: 10.1016/j.actamat.2016.07.029 | |
"Improvement of aging kinetics and precipitate size refinement in Mg-Sn alloys by hafnium additions" L. Zhou, H.B. Henderson, M.V. Manuel, Y. Sohn, A. Agarwal, B. Boesl, S. Behdad, [2016] Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing · DOI: 10.1016/j.msea.2015.11.043 | |
"Interdiffusion in Ternary Magnesium Solid Solutions of Aluminum and Zinc" N. S. Kulkarni, B. Warmack, Y. H. Sohn, C. C. Kammerer, [2016] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-015-0438-7 | |
"Microstructural development from interdiffusion and reaction between U-Mo and AA6061 alloys annealed at 600 degrees and 550 degrees C" D.D. Keiser, Y.H. Sohn, E. Perez, [2016] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2016.05.019 | |
"Diffusion kinetics, mechanical properties, and crystallographic characterization of intermetallic compounds in the Mg–Zn binary system" S. Behdad, L. Zhou, F. Betancor, M. Gonzalez, B. Boesl, Y.H. Sohn, C.C. Kammerer, [2015] Intermetallics · DOI: 10.1016/j.intermet.2015.08.001 | |
"Diffusion kinetics, mechanical properties, and crystallographic characterization of intermetallic compounds in the Mg-Zn binary system" S. Behdad, L. Zhou, F. Betancor, M. Gonzalez, B. Boesl, Y.H. Sohn, C.C. Kammerer, [2015] Intermetallics · DOI: 10.1016/j.intermet.2015.08.001 | |
"Microstructural anomalies in hot-isostatic pressed U–10 wt.% Mo fuel plates with Zr diffusion barrier" N. Eriksson, D.D. Keiser, J.F. Jue, B. Rabin, G. Moore, Y.H. Sohn, Y. Park, [2015] Materials Characterization · DOI: 10.1016/j.matchar.2015.03.015 | |
"Microstructural anomalies in hot-isostatic pressed U-10 wt.% Mo fuel plates with Zr diffusion barrier" N. Eriksson, D.D. Keiser, J.F. Jue, B. Rabin, G. Moore, Y.H. Sohn, Y. Park, [2015] Materials Characterization · DOI: 10.1016/j.matchar.2015.03.015 | |
"Diffusional Interaction Between U-10 wt pct Zr and Fe at 903 K, 923 K, and 953 K (630 A degrees C, 650 A degrees C, and 680 A degrees C)" K. Huang, A. Paz y Puente, H. S. LEE, B. H. Sencer, J. R. Kennedy, Y. H. Sohn, Y. Park, [2015] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-014-2277-2 | |
"Failure characteristics and mechanisms of EB-PVD TBCs with Pt-modified NiAl bond coats" Sriparna Mukherjee, Ke Huang, Young Whan Park, Yongho Sohn, Le Zhou, [2015] Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing · DOI: 10.1016/j.msea.2015.03.120 | |
"Interdiffusion and reactions between U-Mo and Zr at 650 degrees C as a function of time" D.D. Keiser, Y.H. Sohn, Y. Park, [2015] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2014.09.040 | |
"Magnetocaloric response of non-stoichiometric Ni2MnGa alloys and the influence of crystallographic texture" A.K. Giri, B.A. Paterson, C.L. Dennis, L. Zhou, S.C. Vogel, O. Gourdon, H.M. Reiche, K.C. Cho, Y.H. Sohn, R.D. Shull, B.S. Majumdar, M.V. McLeod, [2015] Acta Materialia · DOI: 10.1016/j.actamat.2015.06.059 | |
"Martensitic transformation and mechanical properties of Ni49+xMn36-xIn15 (x=0, 0.5, 1.0, 1.5 and 2.0) alloys" Abhishek Mehta, Anit Giri, Kyu Cho, Yongho Sohn, Le Zhou, [2015] Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing · DOI: 10.1016/j.msea.2015.08.034 | |
"Microstructural Development and Ternary Interdiffusion in Ni-Mn-Ga Alloys" Catherine Kammerer, Anit Giri, Kyu Cho, Yongho Sohn, Le Zhou, [2015] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-015-3123-x | |
"Nanostructured tungsten through cryogenic attrition" Frank Kellogg, Clara Hofmeister, Anit Giri, Kyu Cho, Yongho Sohn, Le Zhou, [2015] International Journal of Refractory Metals & Hard Materials · DOI: 10.1016/j.ijrmhm.2015.05.016 | |
"Quantification of nitrogen impurity and estimated Orowan strengthening through secondary ion mass spectroscopy in aluminum cryomilled for extended durations" Mikhail Klimov, Tim Deleghanty, Kyu Cho, Yongho Sohn, Clara Hofmeister, [2015] Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing · DOI: 10.1016/j.msea.2015.09.007 | |
"Radiation effects on interface reactions of U/Fe, U/(Fe plus Cr), and U/(Fe plus Cr plus Ni)" Di Chen, Chaochen Wei, Michael S. Martin, Xuemei Wang, Youngjoo Park, Ed Dein, Kevin R. Coffey, Yongho Sohn, Bulent H. Sencer, J. Rory Kennedy, Lin Shao, [2015] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2014.09.046 | |
"Corrosion Behaviour of AISI 304 Stainless Steel with Solar Salt Heat Transfer Fluid"
Le Zhou, Nahid Mohajeri, Yong Ho Sohn, Omar Ahmed,
[2014]
Advanced Materials Research
· DOI: 10.4028/www.scientific.net/amr.922.13
In an effort to understand the compatibility between the heat transfer medium and the structural materials used in concentrated solar power plants, the corrosion behavior of AISI 304 stainless steel (18 wt.% Cr, 8 wt.% Ni) in a molten solar salt mixture (53 wt. % KNO3, 40 wt. % NaNO2,7 wt. % NaNO3) has been investigated. The 304 stainless steel coupon samples were fully immersed and isothermally exposed to solar salt at 530°C for 250, 500, and 750 hours in air. X-ray diffraction and scanning electron microscopy with X-ray energy-dispersive spectroscopy were employed to examine the extent of corrosion and identify the corrosion products. Oxides of iron were found to be the primary corrosion products in the presence of the molten alkali nitrates-nitrite salt mixture because of the dissolution of the protective chromium oxide (Cr2O3) scale formed on 304 stainless steel coupons. The corrosion scale was uniform in thickness and chromium-iron oxide was found near the AISI 304. This indicates that the scale formed, particularly on the upper layer with presence of sodium-iron-oxide is protective, and forms an effective barrier against penetration of fused solar salt. By extrapolation, annual corrosion rate is estimated to reach 0.784 mils per year. Corrosion behavior of AISI 304 stainless steel is discussed in terms of thermodynamics and reaction paths. |
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"Investigation of interdiffusion behavior in the Mo-Zr binary system via diffusion couple studies" J. Dickson, D.D. Keiser, Y.H. Sohn, A. Paz y Puente, [2014] International Journal of Refractory Metals & Hard Materials · DOI: 10.1016/j.ijrmhm.2013.12.017 | |
"Diffusion Barrier Selection from Refractory Metals (Zr, Mo and Nb) Via Interdiffusion Investigation for U-Mo RERTR Fuel Alloy" C. C. Kammerer, D. D. Keiser, Y. H. Sohn, K. Huang, [2014] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-013-0270-x | |
"Effects of Cr and Ni on interdiffusion and reaction between U and Fe-Cr-Ni alloys" Y. Park, L. Zhou, K.R. Coffey, Y.H. Sohn, B.H. Sencer, J.R. Kennedy, K. Huang, [2014] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2014.04.009 | |
"Growth kinetics and microstructural evolution during hot isostatic pressing of U-10 wt.% Mo monolithic fuel plate in AA6061 cladding with Zr diffusion barrier" J. Yoo, K. Huang, D.D. Keiser, J.F. Jue, B. Rabin, G. Moore, Y.H. Sohn, Y. Park, [2014] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2014.01.018 | |
"How Fundamentals of Phase Equilibria and Diffusion Contribute to the RERTR program" Dennis D. Keiser, Yongho Sohn, [2014] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-013-0272-8 | |
"Interdiffusion and impurity diffusion in polycrystalline Mg solid solution with Al or Zn" N.S. Kulkarni, R.J. Warmack, Y.H. Sohn, C.C. Kammerer, [2014] Journal of Alloys and Compounds · DOI: 10.1016/j.jallcom.2014.07.193 | |
"Interdiffusion and reaction between Zr and Al alloys from 425 degrees to 625 degrees C" L. Zhou, A. Paz y Puente, M. Fu, D.D. Keiser, Y.H. Sohn, J. Dickson, [2014] Intermetallics · DOI: 10.1016/j.intermet.2013.12.012 | |
"Overview of SIMS-Based Experimental Studies of Tracer Diffusion in Solids and Application to Mg Self-Diffusion" Robert J. Bruce Warmack, Bala Radhakrishnan, Jerry L. Hunter, Yongho Sohn, Kevin R. Coffey, Graeme E. Murch, Irina V. Belova, Nagraj S. Kulkarni, [2014] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-014-0344-4 | |
"Simultaneous tracer diffusion and interdiffusion in a sandwich-type configuration to provide the composition dependence of the tracer diffusion coefficients" N.S. Kulkarni, Y.H. Sohn, G.E. Murch, I.V. Belova, [2014] Philosophical Magazine · DOI: 10.1080/14786435.2014.965234 | |
"High-temperature mechanical response of A359-SiCp-30%: tensile loading (I)" Justin Karl, Yongho Sohn, Ali P. Gordon, James DeMarco, [2013] Materials At High Temperatures · DOI: 10.3184/096034013x13757200691968 | |
"High-temperature mechanical response of A359-SiCp-30%: torsional loading (II)" Justin Karl, Yongho Sohn, Ali P. Gordon, James DeMarco, [2013] Materials At High Temperatures · DOI: 10.3184/096034013x13757116460599 | |
"Interdiffusion Between Potential Diffusion Barrier Mo and U-Mo Metallic Fuel Alloy for RERTR Applications" Y. Park, D. D. Keiser, Y. H. Sohn, K. Huang, [2013] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-013-0236-z | |
"Interdiffusion, Intrinsic Diffusion, Atomic Mobility, and Vacancy Wind Effect in gamma(bcc) Uranium-Molybdenum Alloy" Dennis D. Keiser, Yongho Sohn, Ke Huang, [2013] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-012-1425-9 | |
"Phase development in a U-7 wt.% Mo vs. Al-7 wt.% Ge diffusion couple" D.D. Keiser, Y.H. Sohn, E. Perez, [2013] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2013.05.069 | |
"Role of Si on the Diffusional Interactions Between U-Mo and Al-Si Alloys at 823 K (550 degrees C)" Yong-Ho Sohn, Dennis D. Keiser, Emmanuel Perez, [2013] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-012-1368-1 | |
"Simultaneous measurement of tracer and interdiffusion coefficients: an isotopic phenomenological diffusion formalism for the binary alloy" N.S. Kulkarni, Y.H. Sohn, G.E. Murch, I.V. Belova, [2013] Philosophical Magazine · DOI: 10.1080/14786435.2013.813982 | |
"Understanding the phase equilibrium and irradiation effects in Fe-Zr diffusion couples" Assel Aitkaliyeva, Zhiping Luo, Ashley Ewh, Y.H. Sohn, J.R. Kennedy, Bulent H. Sencer, M.T. Myers, M. Martin, J. Wallace, M.J. General, Lin Shao, Chao-Chen Wei, [2013] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2012.07.027 | |
"Aluminum Impurity Diffusion in Magnesium" Andrew P. Warren, Kevin R. Coffey, Nagraj Kulkarni, Peter Todd, Mikhail Kilmov, Yongho Sohn, Sarah Brennan, [2012] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-012-0007-2 | |
"Effect of Sc addition on the microstructure and mechanical properties of as-atomized and extruded Al-20Si alloys" Woo-Ram Lee, Tae-Haeng Lee, Yongho Sohn, Soon-Jik Hong, M. Fatih Kilicaslan, [2012] Materials Letters · DOI: 10.1016/j.matlet.2011.12.050 | |
"Interdiffusion Between Zr Diffusion Barrier and U-Mo Alloy" Y. Park, D. D. Keiser, Y. H. Sohn, K. Huang, [2012] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-012-0106-0 | |
"Interdiffusion in the Mg-Al System and Intrinsic Diffusion in beta-Mg2Al3" Katrina Bermudez, Nagraj S. Kulkarni, Yongho Sohn, Sarah Brennan, [2012] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-012-1248-8 | |
"Life approximation of thermal barrier coatings via quantitative microstructural analysis" P. Mohan, K. Lee, B. Yang, J. Suk, S. Choe, Y.H. Sohn, C. Bargraser, [2012] Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing · DOI: 10.1016/j.msea.2012.04.008 | |
"Strain Energy During Mechanical Milling: Part I. Mathematical Modeling" Bo Yao, Zhihui Zhang, Ying Li, Yongho Sohn, Julie M. Schoenung, Enrique J. Lavernia, Yaojun Lin, [2012] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-012-1223-4 | |
"Strain Energy During Mechanical Milling: Part II. Experimental" Bo Yao, Zhihui Zhang, Ying Li, Yongho Sohn, Julie M. Schoenung, Enrique J. Lavernia, Yaojun Lin, [2012] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-012-1221-6 | |
"Strain-induced grain growth of cryomilled nanocrystalline Al in trimodal composites during forging" B. Simkin, B. Majumdar, C. Smith, M. van den Bergh, K. Cho, Y.H. Sohn, B. Yao, [2012] Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing · DOI: 10.1016/j.msea.2011.12.079 | |
"Tailoring Microstructure and Properties of Hierarchical Aluminum Metal Matrix Composites Through Friction Stir Processing" T. Patterson, C. Hofmeister, C. Kammerer, W. Mohr, M. van den Bergh, M. Shaeffer, J. Seaman, K. Cho, Y. H. Sohn, [2012] Jom · DOI: 10.1007/s11837-012-0249-9 | |
"Characterization of Interaction Layer in U-Mo-X (X = Nb, Zr) and U-Nb-Zr vs. Al Diffusion Couples Annealed at 600°C for 10 Hours"
E. Perez, Dennis D. Keiser, Yong Ho Sohn, Ashley Ewh,
[2011]
Defect and Diffusion Forum
· DOI: 10.4028/www.scientific.net/ddf.312-315.1055
U-Mo has thus far proven to be one of the most feasible metallic fuel alloys for use in research and test reactors due to its high density and stability during irradiation. However, an adverse diffusional interaction can occur between the fuel alloy and the Al based matrix. This forms an interaction layer (IL) that has undesirable thermal properties and irradiation behavior leading to accelerated swelling and reduced fuel efficiency. This study focused on the effects of ternary alloying additions on the formation of IL between U based alloys and Al. Diffusion couples of U-8Mo-3Nb, U-7Mo-6Zr, and U-10Nb-4Zr (wt.%) vs. pure Al were assembled and annealed at 600°C for 10 hours. Both thickness and phase constituent analyses were performed via electron microscopy. The major phase constituent of the IL was determined to be the UAl3 intermetallic compound. The Nb and Zr alloying additions did not reduce growth rate of IL (1.3~1.4 m/sec1/2) as compared to couples made between binary U-Mo and Al (0.9~1.8 m/sec1/2). |
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"Continuous Strip Casting, Microstructure and Properties of Au-Sn Soldering Alloy" Young-Min Jin, Yong-ho Sohn, Jung Namkung, Mun-Chul Kim, Kee-Ahn Lee, [2011] Metals and Materials International · DOI: 10.1007/s12540-011-0202-4 | |
"Hollow-cone dark-field transmission electron microscopy for dislocation density characterization of trimodal Al composites" Helge Heinrich, Cory Smith, Mark van den Bergh, Kyu Cho, Yong-ho Sohn, Bo Yao, [2011] Micron · DOI: 10.1016/j.micron.2010.08.010 | |
"Microstructural characterization of U-7Mo/Al-Si alloy matrix dispersion fuel plates fabricated at 500 degrees C" Jan-Fong Jue, Bo Yao, Emmanuel Perez, Yongho Sohn, Curtis R. Clark, Dennis D. Keiser, [2011] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2011.02.027 | |
"Microstructure characterization of as-fabricated and 475 degrees C annealed U-7 wt.% Mo dispersion fuel in Al-Si alloy matrix" Emmanuel Perez, Dennis D. Keiser, Jan-Fong Jue, Curtis R. Clark, Nicolas Woolstenhulme, Yongho Sohn, Bo Yao, [2011] Journal of Alloys and Compounds · DOI: 10.1016/j.jallcom.2011.07.048 | |
"Phase Constituents and Microstructure of Interaction Layer Formed in U-Mo Alloys vs Al Diffusion Couples Annealed at 873 K (600 A degrees C)" D. D. Keiser, Y. H. Sohn, E. Perez, [2011] Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science · DOI: 10.1007/s11661-011-0733-9 | |
"Thermotransport in gamma(bcc) U-Zr alloys: A phase-field model study" J. Bush, M.A. Okuniewski, Y.H. Sohn, R.R. Mohanty, [2011] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2011.03.028 | |
"Determination of Average Ternary Interdiffusion Coefficients Using Moments of Interdiffusion Flux and Concentration Profiles"
H.J. Choi, Yong Ho Sohn, N. Garimella,
[2010]
Defect and Diffusion Forum
· DOI: 10.4028/www.scientific.net/ddf.297-301.1328
We developed a method of rigorous solution of the Onsager’s flow equations using moments of the interdiffusion-parameter integrands for the determination of average ternary interdiffusion coefficients. The analysis developed by Dayananda and Sohn [1] is the basis for this refined approach. Average main and cross interdiffusion coefficients are determined over selected regions in the diffusion zone using the diffusion-distance moments of the interdiffusion flux flow equations. Thermodynamic stability of solid solutions in the light of interdiffusion phenomenon is taken as validation criteria to identify accurate and reliable values of the ternary interdiffusion coefficients. Regulations are proposed for successful application of the analysis method to various ternary diffusion couples in Ni- and Fe-based intermetallics. |
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"Site Preference and Diffusion in Ni3Al Alloyed with Ir, Ta or Re at 1200°C"
H.J. Choi, Yong Ho Sohn, N. Garimella,
[2010]
Defect and Diffusion Forum
· DOI: 10.4028/www.scientific.net/ddf.297-301.1322
Diffusion in L12-Ni3Al with ternary alloying additions of Ir, Ta and Re was investigated at 1200°C using solid-to-solid diffusion couples, and examined with respect to site preference in ordered intermetallic compound. In addition to determination of average ternary interdiffusion coefficients [1-3], average effective interdiffusion coefficients were determined directly from the experimental concentration profiles. Ni has the largest magnitude of average effective interdiffusion coefficient, followed by Al, Ir, Re and Ta. The average effective interdiffusion coefficients for Ir, Re and Ta are much smaller than those for Ni and Al. Tracer diffusion coefficients determined by extrapolation technique, and available literature also followed the same trend. The relative tendency of Ni, Al, Ir, Re and Ta to occupy the -Ni and -Al sites are correlated to these diffusion coefficients, with due consideration for diffusion mechanisms and coordination of atoms. |
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"Composition and structure of nitrogen-containing dispersoids in trimodal aluminum metal-matrix composites" B. Yao, Y. H. Sohn, T. Delahanty, M. van den Bergh, K. Cho, C. Hofmeister, [2010] Journal of Materials Science · DOI: 10.1007/s10853-010-4571-8 | |
"Degradation of Thermal Barrier Coatings by Fuel Impurities and CMAS: Thermochemical Interactions and Mitigation Approaches" Travis Patterson, Bo Yao, Yongho Sohn, Prabhakar Mohan, [2010] JOURNAL OF THERMAL SPRAY TECHNOLOGY · DOI: 10.1007/s11666-009-9424-0 | |
"Microstructural Characterization of U-Nb-Zr, U-Mo-Nb, and U-Mo-Ti Alloys via Electron Microscopy" E. Perez, D. D. Keiser, Y. H. Sohn, A. Ewh, [2010] Journal of Phase Equilibria and Diffusion · DOI: 10.1007/s11669-009-9645-4 | |
"Microstructural analysis of as-processed U-10 wt.%Mo monolithic fuel plate in AA6061 matrix with Zr diffusion barrier" B. Yao, D.D. Keiser, Y.H. Sohn, E. Perez, [2010] Journal of Nuclear Materials · DOI: 10.1016/j.jnucmat.2010.04.016 | |
"Microstructural features influencing the strength of Trimodal Aluminum Metal-Matrix-Composites" Clara Hofmeister, Travis Patterson, Yong-ho Sohn, Mark van den Bergh, Tim Delahanty, Kyu Cho, Bo Yao, [2010] Composites Part a-Applied Science and Manufacturing · DOI: 10.1016/j.compositesa.2010.02.013 | |
"Transmission electron microscopy observations on the phase composition and microstructure of the oxidation scale grown on as-polished and yttrium-implanted beta-NiAl" J. Jedlinski, B. Yao, Y.H. Sohn, H.J. Choi, [2010] Surface & Coatings Technology · DOI: 10.1016/j.surfcoat.2010.10.034 | |
"Selected Observations in Phase Constituents, Growth Kinetics and Microstructural Development of Aluminides in U-Mo vs. Al and 6061 Diffusion Couples Annealed at 600°C"
Dennis D. Keiser, Yong Ho Sohn, E. Perez,
[2009]
Defect and Diffusion Forum
· DOI: 10.4028/www.scientific.net/ddf.289-292.41
This paper presents selected experimental observations of phase constituents, growth kinetics, and microstructural development of aluminide phases that develop in solid-to-solid diffusion couples assembled with U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. Al and 6061 alloy after a diffusion anneal at 600°C for 24 hours. Scanning electron microscopy coupled with energy dispersive spectroscopy, electron microprobe analysis, and transmission electron microscopy via focused ion beam in-situ lift-out were employed to characterize the interaction layer that develops by interdiffusion. While concentration profiles exhibited no significant gradients, microstructural analysis revealed the presence of extremely complex and nano-scale phase constituents with presence of orthorhombic--U, cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43 and diamond cubic-UMo2Al20 phases. Presence of multi-phase layers with microstructure, which suggest a significant role of grain boundary diffusion, was observed. |
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"Diffusion under temperature gradient: A phase-field model study"
J. E. Guyer, Y. H. Sohn, R. R. Mohanty,
[2009]
JOURNAL OF APPLIED PHYSICS
· DOI: 10.1063/1.3190607
A diffuse interface model was devised and employed to investigate the effect of thermotransport (a.k.a., thermomigration) process in single-phase and two-phase alloys of a binary system. Simulation results show that an applied temperature gradient can cause significant redistribution of constituent elements and phases in the alloy. The magnitude and the direction of the redistribution depend on the initial composition, the atomic mobility and the heat of transport of the respective elements. In two-phase alloys, the thermomigration effect can cause the formation of single-element rich phases at the cold and hot ends of the alloy (i.e., demixing). |
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"Effect of hydrogen on the physical and mechanical properties of silicon carbide-derived carbon films" Heung-Taek Bae, Michael J. McNallan, Yong-Ho Sohn, Dae-Soon Lim, Hyun-Ju Choi, [2009] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2009.05.023 | |
"Electrophoretically deposited alumina as protective overlay for thermal barrier coatings against CMAS degradation" B. Yao, T. Patterson, Y.H. Sohn, P. Mohan, [2009] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2009.09.055 | |
"Interdiffusion in L1(2)-Ni3Al Alloyed with Re" M. Ode, M. Ikeda, H. Murakami, Y. H. Sohn, N. Garimella, [2009] JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION · DOI: 10.1007/s11669-009-9499-9 | |
"Phase constituents of Al-rich U-Mo-Al alloys examined by transmission electron microscopy" A. Ewh, J. Liu, B. Yuan, D.D. Keiser, Y.H. Sohn, E. Perez, [2009] JOURNAL OF NUCLEAR MATERIALS · DOI: 10.1016/j.jnucmat.2009.09.003 | |
"Degradation of Yttria Stabilized Zirconia Thermal Barrier Coatings by Molten CMAS (CaO-MgO-Al2O3-SiO2) Deposits"
Biao Yuan, Travis Patterson, Vimal Desai, Yong Ho Sohn, Prabhakar Mohan,
[2008]
Materials Science Forum
· DOI: 10.4028/www.scientific.net/msf.595-598.207
In advanced gas turbine engines that operate in a dust-laden environment causing ingestion of siliceous debris into engines, thermal barrier coatings (TBCs) are highly susceptible to degradation by molten CMAS (calcium-magnesium alumino silicate) deposits. In this study, the degradation mechanisms other than the commonly reported thermomechanical damage are investigated with an emphasis on the thermochemical aspects of molten CMAS induced degradation of TBCs. Free-standing yttria stabilized zirconia (8YSZ) TBC specimens in contact with a model CMAS composition were subjected to isothermal heat treatment in air at temperatures ranging from 1200°C to 1350°C. Phase transformations and microstructural development were examined by using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Starting at 1250°C, the molten CMAS readily infiltrated and dissolved the YSZ coating followed by reprecipitation of zirconia with a different morphology and composition that depends on the local melt chemistry. Significant amount of Y2O3 depleted monoclinic ZrO2 phase evolved from CMAS melt that dissolved ť-ZrO2 was evident. Thus the mechanism of dissolution and reprecipitation due to molten CMAS damage resulted in destabilization of the YSZ with disruptive phase transformation (t’ f + m). |
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"Phase Field Modeling of Interdiffusion Microstructure in Ni-Cr-Al Diffusion Couples"
Yong Ho Sohn, R.R. Mohanty,
[2008]
Materials Science Forum
· DOI: 10.4028/www.scientific.net/msf.595-598.199
Evolution of interdiffusion microstructures was examined in ternary Ni-Cr-Al solid-tosolid diffusion couples using two-dimensional (2D) phase field simulation. Utilizing Cahn-Hilliard and Allen-Cahn equations, multiphase diffusion couples containing of fcc-γ and B2-β solid solution phases were simulated with alloys of different compositions and phase contents. Chemical mobility as a function of composition with constant gradient energy coefficients was used in the simulation. Simulated microstructures in γ+β/γ and γ+β/γ+β diffusion couples were compared with the experimental microstructures reported in literature. As observed experimentally, the model predicted the recession of γ+β region in the γ+β/γ couple and a stationary interface in γ+β/γ+β couple. Concentration profiles developed across the diffusion couples demonstrated that the interdiffusion occurs in the γ phase as well as in the γ+β region. Formation of single-phase γ and β layers near the interface of γ+β/γ+β couples was also investigated using the volume fraction profile obtained from the simulated microstructure. |
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"Ternary and Quaternary Interdiffusion in γ (fcc) Fe-Ni-Cr-X (X = Si, Ge) Alloys at 900°C"
M.P. Brady, Yong Ho Sohn, N. Garimella,
[2008]
Materials Science Forum
· DOI: 10.4028/www.scientific.net/msf.595-598.1145
Interdiffusion in Fe-Ni-Cr (fcc γ phase) alloys with small additions of Si and Ge at 900°C was studied using solid-to-solid diffusion couples. Alloy rods of Fe-24 at.%Ni, Fe-24 at.%Ni- 22at.%Cr, Fe-24 at.%Ni-22at.%Cr-4at.%Si and Fe-24 at.%Ni-22at.%Cr-1.7at.%Ge were cast using arc-melt, and homogenized at 900°C for 168 hours. Sectioned alloy disks from the rods were polished, and diffusion couples were assembled with in Invar steel jig, encapsulated in Argon after several hydrogen flushes, and annealed atz 900°C for 168 hours. Polished cross-sections of the diffusion couples were characterized to determine experimental concentration profiles using electron probe microanalysis with pure elemental standards. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion flux profiles were examined to determine the average ternary and quaternary interdiffusion coefficients. Effects of alloying additions on the interdiffusional behavior of Fe-Ni- Cr-X alloys at 900°C are presented with due consideration for the formation of protective Cr2O3 scale. |
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"Ternary Interdiffusion in L12-Ni3Al with Ir Alloying Addition"
N. Garimella, Muneaki Ikeda, Hideyuki Murakami, Yong Ho Sohn, Machiko Ode,
[2008]
Defect and Diffusion Forum
· DOI: 10.4028/www.scientific.net/ddf.273-276.637
Average ternary interdiffusion coefficients in Ni3Al with Ir additions have been determined using solid-to-solid diffusion couples annealed at 1200°C for 5 hours. Disc shaped alloy specimens were prepared by the vacuum arc melting at compositions of Ni-24Al, Ni-25Al, Ni-26Al, Ni-23.5Al-1Ir, Ni-24.5Al-1Ir, Ni-23Al-2Ir, Ni-23Al-2Ir, Ni-24Al-2Ir, Ni-23Al-3Ir (at.%). Surfaces of alloys were polished down to 1200 grit and diffusion couples were assembled in Si3N4 jig for initial bonding heat treatment at 1200°C for 0.5 hours. Additional diffusion anneal was carried out at 1200°C for 4.5 hours outside of Si3N4 jig so that diffusion couples can be water quenched. Concentration profiles of individual components were measured by electron probe microanalysis using pure standard of Ni, Al and Ir. Interdiffusion flux of individual component was determined directly from the experimental concentration profiles, and the moments of interdiffusion flux were examined to calculate the average ternary interdiffusion coefficients, D˜ ij k either with Al or Ni as dependent component. Calculated interdiffusion coefficients suggest that Ir-alloyed Al2O3-forming oxidation resistant coatings would be beneficial to reduce the interdiffusion flux of Ni from superalloy substrates to the coating, and reduce the interdiffusion flux of Al from the coating to the superalloy substrate. |
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"A simplistic model to study the influence of film cooling on low temperature hot corrosion rate in coal gas/syngas fired gas turbines" Sanjeev Bharani, J.S. Kapat, Y.H. Sohn, V.H. Desai, Vaidyanathan Krishnan, [2008] International Journal of Heat and Mass Transfer · DOI: 10.1016/j.ijheatmasstransfer.2007.05.017 | |
"Degradation of free-standing air plasma sprayed CoNiCrAlY coatings by vanadium and phosphorus pentoxides" T. Patterson, V.H. Desai, Y.H. Sohn, P. Mohan, [2008] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2008.08.068 | |
"Effe-as of Ir or Ta alloying addition on interdiffusion of L1(2)-Ni3Al" M. Ode, M. Ikeda, H. Murakami, Y.H. Sohn, N. Garimella, [2008] INTERMETALLICS · DOI: 10.1016/j.intermet.2008.06.011 | |
"Microstructural stability of fcc-gamma+B2-beta coatings on gamma substrate in Ni-Cr-Al system - A phase field model study" Y.H. Sohn, R.R. Mohanty, [2008] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2008.07.023 | |
"Phase-field simulation of interdiffusion microstructure containing fcc-gamma and L1(2)-gamma ' phases in Ni-Al diffusion couples" A. Leon, Y.H. Sohn, R.R. Mohanty, [2008] COMPUTATIONAL MATERIALS SCIENCE · DOI: 10.1016/j.commatsci.2007.11.002 | |
"Thermal cyclic lifetime and oxidation behavior of air plasma sprayed CoNiCrAlY bond coats for thermal barrier coatings" A. Leon, B. Jayaraj, J. Liu, Y.H. Sohn, T. Patterson, [2008] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2008.08.054 | |
"Thermal stability, microstructure and mechanical properties of nanostructured Al-Ni-Mm-X (X = Cu and Fe) alloys hot-extruded from gas-atomized powders" [2008] MATERIALS TRANSACTIONS · DOI: 10.2320/matertrans.mra200763 | |
"Diffusion in Advanced Materials and Processing" C. Campbell, D. Lewis, Afina Lupulescu, Yong Ho Sohn, [2007] · DOI: 10.4028/b-bss9qy | |
"Microstructural Evolution of Durable Thermal Barrier Coatings with Hf and/or Y Modified CMSX-4TM Superalloy Substrates"
Yong Ho Sohn, K.S. Murphy, J. Liu,
[2007]
Materials Science Forum
· DOI: 10.4028/www.scientific.net/msf.539-543.1206
Thermal cyclic lifetime and microstructural degradation of thermal barrier coatings (TBCs) with (Ni,Pt)Al bond coat and Hf- and/or Y-modified CSMX-4 superalloy substrates were examined. Thermal cyclic lifetime of TBCs was measured using a furnace thermal cycle test that consisted of 10-minute heat-up, 50-minute dwell at 1135°C, and 10-minute forced-air-quench. TBC lifetime was observed to improve from 600 cycles to over 3200 cycles with appropriate Hf- and/or Y-alloying of CMSX-4 superalloys. This significant improvement in TBC lifetime is the highest reported lifetime in literature with similar testing parameters. Cross-sectional microstructure of TBC specimens were examined by scanning electron microscopy (SEM) after the spallation failure. While undulation of TGO/bond coat interface (e.g., rumpling and racheting) was observed to be main damage mechanisms for TBCs on baseline CMSX-4, the same interface remained relatively flat for durable TBCs on Hf- and/or Y-modified CSMX-4. The parabolic growth constant of the TGO scale was slightly lower for TBCs with Hfand/ or Y-modified CSMX-4. |
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"Degradation of yttria-stabilized zirconia thermal barrier coatings by vanadium pentoxide, phosphorous pentoxide, and sodium sulfate"
Biao Yuan, Travis Patterson, Vimal H. Desai, Yongho H. Sohn, Prabhakar Mohan,
[2007]
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
· DOI: 10.1111/j.1551-2916.2007.01941.x
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"Microstructure and residual stress of alumina scale formed on Ti2AlC at high temperature in air" J. Liu, M. Hopkins, W. Fischer, N. Garimella, K. B. Park, M. P. Brady, M. Radovic, T. El-Raghy, Y. H. Sohn, J. W. Byeon, [2007] OXIDATION OF METALS · DOI: 10.1007/s11085-007-9063-0 | |
"Size dependent study of MeOH decomposition over size-selected pt nanoparticles synthesized via micelle encapsulation" Simon Mostafa, Jing Liu, Yong-ho Sohn, Beatriz Roldan Cuenya, Jason R. Croy, [2007] Catalysis Letters · DOI: 10.1007/s10562-007-9162-1 | |
"Support dependence of MeOH decomposition over size-selected Pt nanoparticles" Simon Mostafa, Jing Liu, Yongho Sohn, Helge Heinrich, Beatriz Roldan Cuenya, Jason R. Croy, [2007] Catalysis Letters · DOI: 10.1007/s10562-007-9236-0 | |
"Integrated, Effective and Average Interdiffusion Coefficients and their Applications in Multicomponent Alloys for Energy Production Technologies"
N. Garimella, E. Perez, R.R. Mohanty, J. Liu, Yong Ho Sohn,
[2006]
Defect and Diffusion Forum
· DOI: 10.4028/www.scientific.net/ddf.258-260.346
Solid-state diffusion is a subject of great interest for many intellectual merits and practical applications. It also provides excellent educational studies with cross-fertilization of science and technology. This paper examines the importance of multicomponent-multiphase interdiffusion with specific examples from materials and coatings for components in advanced energy production systems, including gas turbines and nuclear reactors. Results and analysis from laboratory experiments are presented in terms of interdiffusion fluxes, integrated interdiffusion coefficients, effective interdiffusion coefficients, and average multicomponent interdiffusion coefficients. Applications are highlighted for materials and coatings for components in advanced energy production technologies. Additional consideration is given to the refined approach to assess composition-dependent interdiffusion coefficients in multicomponent alloys. |
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"Al-2(Mg,Ca) phases in Mg-Al-Ca ternary system: First-principles prediction and experimental identification" Jing Liu, Ron A. Witt, Yong-ho Sohn, Zi-Kui Liu, Yu Zhong, [2006] SCRIPTA MATERIALIA · DOI: 10.1016/j.scriptamat.2006.03.068 | |
"Changes in electrochemical impedance with microstructural development in TBCs" [2006] JOM | |
"Effects of phase constituents/microstructure of thermally grown oxide on the failure of EB-PVD thermal barrier coating with NiCoCrAlY bond coat" J.W. Byeon, Y.H. Sohn, J. Liu, [2006] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2005.08.140 | |
"Interdiffusion analysis for NiAl versus superalloys diffusion couples" T. Patterson, Y. Sohn, E. Perez, [2006] JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION · DOI: 10.1361/154770306x153701 | |
"Interdiffusion in gamma (face-centered cubic) Ni-Cr-X (X = Al, Si, Ge, or Pd) alloys at 900 degrees C" M.P. Brady, Yongho Sohn, Narayana Garimella, [2006] Journal of Phase Equilibria and Diffusion · DOI: 10.1361/154770306x153710 | |
"Oxygen diffusion through Al-doped amorphous SiO2" Yongho Sohn, Yi Fan, Ligong Zhang, Linan An, Yiguang Wang, [2006] JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION · DOI: 10.1361/154770306x153729 | |
"Phase-field investigation of multicomponent diffusion in single-phase and two-phase diffusion couples" Y. Sohn, R.R. Mohanty, [2006] Journal of Phase Equilibria and Diffusion · DOI: 10.1361/154770306x153738 | |
"Characterization of Isothermally Oxidized ZrO2-8wt.%Y2O3 Thermal Barrier Coatings by Electrochemical Impedance Spectroscopy"
B. Jayaraj, Yong Ho Sohn, Jai Won Byeon,
[2005]
Materials Science Forum
· DOI: 10.4028/www.scientific.net/msf.486-487.145
Electrochemical impedance spectroscopy was employed to examine ZrO2-8wt.%Y2O3 (yttria stabilized zirconia, YSZ) thermal barrier coating (TBC) as a function of isothermal exposure time at 1121°C. Electrochemical impedance response (resistance and capacitance of YSZ and thermally grown oxide (TGO)) of TBC specimens was analyzed with an alternative current equivalent circuit based on the multi-layered micro-constituents of TBC, and the impedance response was correlated with microstructural changes attributed to isothermal oxidation. The resistance of YSZ was observed to increase initially and then decrease with thermal exposure. The initial increase was related to the high temperature sintering of YSZ, and the subsequent decrease was discussed in terms of microcrack initiation and electrolyte penetration. The TGO thickness was linearly correlated to the capacitance of TGO. |
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"Characterization of Long-Term Oxidized Nickel Aluminide Coating by Photoluminescence Spectroscopy"
N. Mu, J. Liu, Yong Ho Sohn, Jai Won Byeon,
[2005]
Materials Science Forum
· DOI: 10.4028/www.scientific.net/msf.486-487.141
Microstructures and residual stress of long-term oxidized nickel aluminide coating on superalloy were evaluated by photostimulated luminescence spectroscopy (PSLS). CMSX-4 superalloy coupons coated with single phase b-NiAl were oxidized in air at 788, 871, 954 and 1010°C for up to 10000 hours. The photoluminescence technique was applied for the analysis of the phase constituents and the residual stress of the thermally grown oxide (TGO) scale formed on the^coating, together with transmission electron microscopy. According to the PSLS analysis, TGO consisted of both stable a-Al2O3 and metastable Al2O3 phases in specimens oxidized at 788°C and 871°C. At higher temperatures, the TGO scale primarily consisted of equilibrium a-Al2O3. The compressive residual stress within TGO increased up to about 3GPa with increasing oxidation temperature and time until local spallation, after which a decrease as well as large standard deviation of residual stress was observed owing to the stress-relief associated with TGO scale spallation. |
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"Transmission Electron Microscopy of Isothermally Oxidized EB-PVD Thermal Barrier Coating on (Ni,Pt)Al Bondcoat"
S. Laxman, Yong Ho Sohn, Jai Won Byeon,
[2005]
Materials Science Forum
· DOI: 10.4028/www.scientific.net/msf.486-487.149
The growth and microstructure of the thermally grown oxide (TGO) underneath the electron beam physical vapor deposited (EB-PVD) yttria stabilized zirconia (YSZ) topcoat were examined after short-term isothermal oxidation (1100 °C, up to 50 hours) for the as-coated and gritblasted (Ni,Pt)Al bondcoats. Microstructural analysis was carried out by a high resolution scanning transmission electron microscope equipped with bright/dark field imaging, high angle annular dark field imaging, and nano-spot energy dispersive spectroscopy. Presence of mixed oxide zone (MOZ) and a continuous Al2O3 oxide zone (COZ) was observed on the thermal barrier coating (TBC) with the as-coated (Ni,Pt)Al bondcoat. However, on the TBC with grit-blasted bondcoat, only the continuous-columnar Al2O3 scale was observed. For the as-coated type bondcoat, numerous voids were observed near the interface between MOZ and COZ after isothermal oxidation. On the other hand, COZ showed parabolic growth without any formation of voids for the grit-blasted specimens. |
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"Characterization of isothermally oxidized ZrO2-8wt.%Y2O3 thermal barrier coatings by electrochemical impedance spectroscopy" [2005] ECO-MATERIALS PROCESSING & DESIGN VI | |
"Correlation of magnetic Barkhausen emission profile with strength of thermally degraded 2.25chromium-1molybdenum steel" [2005] Materials Transactions | |
"Interdiffusion structures and paths for multiphase Fe-Ni-Al diffusion couples at 1000 degrees C" [2005] METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE | |
"Monitoring damage evolution in thermal barrier coatings with thermal wave imaging" Y.H. Sohn, X. Chen, J.R. Price, Z. Mutasim, B. Franke, [2005] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2005.07.090 | |
"Non-destructive evaluation of degradation in multi-layered thermal barrier coatings by electrochemical impedance spectroscopy" B. Jayaraj, S. Vishweswaraiah, S. Rhee, V.H. Desai, Y.H. Sohn, J.W. Byeon, [2005] MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING · DOI: 10.1016/j.msea.2005.07.004 | |
"A microstructural observation of near-failure thermal barrier coating: a study by photostimulated luminescence spectroscopy and transmission electron microscopy" Y.H. Sohn, S.K. Jha, S. Laxman, R.R. Vanfleet, J. Kimmel, B.W. Kempshall, [2004] THIN SOLID FILMS · DOI: 10.1016/j.tsf.2004.02.046 | |
"Al-O-N based duplex coating system for improved oxidation resistance of superalloys and NiCrAlY coatings" Y.H. Sohn, S. Sastri, N. Gunda, J.A. Haynes, S.K. Jha, [2004] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2003.09.044 | |
"Constituent redistribution in U-Pu-Zr fuel during irradiation" G.L Hofman, S.L Hayes, Y.H Sohn, Yeon Soo Kim, [2004] JOURNAL OF NUCLEAR MATERIALS · DOI: 10.1016/j.jnucmat.2004.01.012 | |
"Electrochemical impedance spectroscopy of porous ZrO2-8 wt.% Y2O3 and thermally grown oxide on nickel aluminide" V.H. Desai, C.K. Lee, Y.H. Sohn, B. Jayaraj, [2004] MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING · DOI: 10.1016/j.msea.2004.01.005 | |
"Electrochemical impedance spectroscopy of thermal barrier coatings as a function of isothermal and cyclic thermal exposure" S. Vishweswaraiah, V.H. Desai, Y.H. Sohn, B. Jayaraj, [2004] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2003.08.092 | |
"Long-term oxidation and phase transformations in aluminized CMSX-4 superalloys" J. Liu, J.W. Byeon, Y.H. Sohn, Y.L. Nava, N. Mu, [2004] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2004.07.091 | |
"Microstructure of as-coated thermal barrier coatings with varying lifetimes" R. Subramanian, B.W. Kempshall, Y.H. Sohn, A.J. Burns, [2004] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2003.06.021 | |
"Phase transformations of thermally grown oxide on (Ni,Pt)Al bondcoat during electron beam physical vapor deposition and subsequent oxidation" B Franke, B.W Kempshall, Y.H Sohn, L.A Giannuzzi, K.S Murphy, S Laxman, [2004] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/j.surfcoat.2003.08.072 | |
"Silicoaluminum carbonitride with anomalously high resistance to oxidation and hot corrosion"
Y. Wang, L. Bharadwaj, L. Zhang, Y. Fan, D. Jiang, Y. Sohn, V.H. Desai, J. Kapat, L.C. Chow, L. An,
[2004]
Advanced Engineering Materials
· DOI: 10.1002/adem.200400010
Due to their excellent thermal and mechanical properties silicon‐based ceramics and composites are prime candidates for high temperature structural applications. In this communication the authors report for the first time that amorphous silicoaluminum carbonitride (SiAlCN) ceramics possess anomalously high resistance to oxidation and hot‐corrosion. A mechanism underlying the observed phenomena is discussed. |
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"The non destructive and nano-microstructural characterization of thermal-barrier coatings" [2004] JOM | |
"Sol gel alumina coating on Fe-Cr-Al-Y fibre media for catalytic converters" [2003] Surface Engineering | |
"The effect of bond coat grit blasting on the durability and thermally grown oxide stress in an electron beam physical vapor deposited thermal barrier coating" Yongho Sohn, Eric H. Jordan, Maurice Gell, Liangde Xie, [2003] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/s0257-8972(03)00466-3 | |
"Diffusion studies in the beta (B-2), beta ' (Bcc), and gamma (Fcc) Fe-Ni-Al alloys at 1000 degrees C" [2002] METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE | |
"Microstructure development of Al2O3-13wt.%TiO2 plasma sprayed coatings derived from nanocrystalline powders" [2002] ACTA MATERIALIA | |
"Phase transformations of plasma-sprayed zirconia-ceria thermal barrier coatings" [2002] JOURNAL OF THE AMERICAN CERAMIC SOCIETY | |
"Development and implementation of plasma sprayed nanostructured ceramic coatings" E.H Jordan, Y.H Sohn, D Goberman, L Shaw, T.D Xiao, M Gell, [2001] SURFACE & COATINGS TECHNOLOGY · DOI: 10.1016/s0257-8972(01)01470-0 | |
"Fabrication and evaluation of plasma sprayed nanostructured alumina-titania coatings with superior properties" M Gell, Y.H Sohn, D Goberman, L Shaw, S Jiang, M Wang, T.D Xiao, Y Wang, P Strutt, E.H Jordan, [2001] MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING · DOI: 10.1016/s0921-5093(00)01382-4 | |
"Microstructural characterization of thermal barrier coatings on high pressure turbine blades" [2001] SURFACE & COATINGS TECHNOLOGY | |
"Thermal cycling of EB-PVD/MCrAlY thermal barrier coatings: 1. Microstructural development and spallation mechanisms" [2001] SURFACE & COATINGS TECHNOLOGY | |
"Thermal cycling of EB-PVD/MCrAlY thermal barrier coatings: II. Evolution of photo-stimulated luminescence" [2001] SURFACE & COATINGS TECHNOLOGY | |
"An Analysis for Interdiffusion Coefficients and Thermotransport Coefficients in Isothermal and Nonisothermal Ternary Diffusion" Yong Ho Sohn, Mysore A. Dayananda, [2000] Solid State Phenomena · DOI: 10.4028/www.scientific.net/ssp.72.99 | |
"A double-serpentine diffusion path for a ternary diffusion couple" [2000] ACTA MATERIALIA | |
"Analysis of constituent redistribution in the gamma (bcc) U-Pu-Zr alloys under gradients of temperature and concentrations" [2000] JOURNAL OF NUCLEAR MATERIALS | |
"Application of Cr(3+)photoluminescence piezo-spectroscopy to plasma-sprayed thermal barrier coatings for residual stress measurement" [2000] MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING | |
"Nondestructive evaluation of residual stress for thermal barrier coated turbine blades by Cr3+ photoluminescence piezospectroscopy" [2000] METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE | |
"A new analysis for the determination of ternary interdiffusion coefficients from a single diffusion couple" [1999] METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE | |
"Bond strength, bond stress and spallation mechanisms of thermal barrier coatings" [1999] SURFACE & COATINGS TECHNOLOGY | |
"Interdiffusion, intrinsic diffusion and vacancy wind effect in Fe-Al alloys at 1000 degrees C" [1998] SCRIPTA MATERIALIA | |
"Average effective interdiffusion coefficients and their applications for isothermal multicomponent diffusion couples" [1996] SCRIPTA MATERIALIA | |
"ISOTHERMAL OXIDATION OF PHYSICAL VAPOR-DEPOSITED PARTIALLY-STABILIZED ZIRCONIA THERMAL BARRIER COATINGS" [1994] JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE | |
"MICROSTRUCTURAL DEVELOPMENT IN PHYSICAL VAPOR-DEPOSITED PARTIALLY-STABILIZED ZIRCONIA THERMAL BARRIER COATINGS" [1994] THIN SOLID FILMS | |
"Characterization of Partially Stabilized Zirconia Thermal Barrier Coatings" R.R. Biederman, Yong Ho Sohn, R.D. Sisson, E.Y. Lee, [1992] Key Engineering Materials · DOI: 10.4028/www.scientific.net/kem.72-74.61 | |
Source: ORCID/CrossRef using DOI |
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