NSUF - Nuclear Science User Facilities

Tianyi Chen

Profile Information
Name
Dr. Tianyi Chen
Institution
Oregon State University
Position
Assistant Professor
h-Index
11
ORCID
0000-0003-2880-824X
Expertise
Accelerator, Diffraction, Electron Backscatter Diffraction, Electron Microscopy, Fracture Mechanics, High Temperature Material, Interface Mechanics And Engineering, Ion Beam Irradiation, Irradiated Microstructure, Molecular Dynamics
Publications:
"Enhanced diffusion of Cr in 20Cr-25Ni type alloys under proton irradiation at 670 °C" Tianyi Chen, ying yang, Li He, Beata Tyburska-Puschel, Kumar Sridharan, Haixuan Xu, Lizhen Tan, Nuclear Materials and Energy Vol. 17 2018 142-146 Link
"High-temperature strengthening mechanisms of Laves and B2 precipitates in a novel ferritic alloy" Tianyi Chen, Chad Parish, Ying Yang, Lizhen Tan, Materials Science and Engineering: A Vol. 720 2018 110-116 Link
Precipitates of the Laves and B2 phases were engineered in a newly-designed advanced ferritic alloy. Under creep test at 650 °C with 120 MPa, the material showed a steady-state minimum creep rate of 1 × 10−4 h−1, about one order of magnitude lower than T91. Microstructural characterization of the ferritic alloy revealed primarily ductile and partially brittle fractures after the creep test. Coarse Laves phase (~ 1 µm) was observed associating with the brittle fracture, resulting in reduced creep ductility. However, fine Laves phase precipitates (~ 100 nm) helped the dimple-ductile fracture and strengthened the material through impeding the motion of dislocations and boundaries. Unlike the B2 precipitates remained coherent exerting the classic Orowan bypassing mechanism at the brittle location, some of the B2 precipitates at the ductile location became incoherent and can develop an attractive interaction with dislocations. This coherency change of B2 precipitates, together with the nucleation of ultrafine (~ 40 nm) Laves phase precipitates during the creep test, would compensate for the coarsening-induced loss of Orowan strengthening of coherent B2 precipitates.
"Intermetallic formation and interdiffusion in diffusion couples made of uranium and single crystal ion" Tianyi Chen, Bulent Sencer, Lin Shao, Travis Smith, Jonathan Gigax, Di Chen, Robert Balerio, Rory Kennedy, Journal of Nuclear Materials Vol. 467 2015 82-88 Link
We studied the interfacial phase formation and diffusion kinetics in uranium–iron diffusion couples. A comparison was made between polycrystalline uranium (U) bonded with polycrystalline iron (FeP) and polycrystalline uranium bonded with single crystalline Fe (FeSC). After thermal annealing at 575 °C, 600 °C, 625 °C and 650 °C, respectively, diffusion and microstructures at the interface were characterized by scanning electron microscopy and transmission electron miscopy. The presence of grain boundaries in iron has a significant influence on interface reactions. In comparison with U–FeP system, interdiffusion coefficients of the U–FeSC system are significantly lower and were governed by much higher activation energies. Integrated interdiffusion coefficients and intrinsic diffusion coefficients were obtained. The intrinsic diffusion coefficients show faster diffusion of iron atoms in both U6Fe and UFe2 intermetallic phases than uranium.
"Microstructural evolution in Fe-20Cr-25Ni austenitic alloys under proton irradiation at 670 ºC" Tianyi Chen, Lizhen Tan, Li He, Beata Tyburska-Puschel, Kumar Sridharan, Transactions of American Nuclear Society Vol. 117 2017 581-583 Link
"Phase Stability in the Fe-Rich Fe-Cr-Ni-Zr Alloys" Tianyi Chen, Lizhen Tan, ying yang, Metallurgical and Materials Transactions A Vol. 48 2017 5009-5016 Link
Knowledge on phase stability in Fe-rich Fe-Cr-Ni-Zr alloys is needed for the development of Laves phase strengthened Fe-Cr-Ni-Zr ferritic alloys. These alloys show promising applications as new cladding materials of nuclear reactors due to enhanced high-temperature strength and resistance to creep and irradiation hardening. Phase stability in four Fe-rich Fe-Cr-Ni-Zr alloys was carefully investigated using scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques. The samples were arc-melted and heat treated at 973.15 K (700 °C) for 1275 hours and 1273.15 K (1000 °C) for 336 hours. The experimental results showed extensive solubility of Ni in the intermetallic phases Fe23Zr6 and Fe2Zr_C15. Nickel stabilizes the Laves Fe2Zr_C15 structure more than the C36 and C14 structures. In addition to Fe23Zr6 and Fe2Zr_C15, Ni7Zr2 was found to be stable in samples with higher Ni content and lower annealing temperature. The Fe2Zr_C15 and Fe23Zr6 coexist with the body-centered cubic matrix phase in all samples regardless of compositions and temperatures.
"Steam oxidation behavior of Ni-base superalloys 690, 725 and X-750 at 600 and 650 °C" Tianyi Chen, Corrosion Science Vol. 157 2019 487-497
The 1-bar steam oxidation behavior of Ni-base superalloys 690, 725, and X-750 was evaluated at 600 and 650 °C for up to 5000 h. In addition to monitoring mass changes, microstructures of the 5000-h-exposed samples were characterized using scanning and transmission electron microscopy and energy dispersive x-ray spectroscopy. Together with thermodynamic calculations, the scale constitution and possible exfoliation was discussed. Alloy X-750 exhibited the best resistance to steam oxidation with the least metal thickness loss at 600 °C while alloy 690 at 650 °C. Alloy 725 exhibited more than two times metal thickness loss than the other two alloys at 650 °C.
"The correlation between microstructure and nanoindentation property of neutron-irradiated austenitic alloy D9" Tianyi Chen, Acta Materialia Vol. 195 2020 1-13 Link
The microstructure and nanomechanical properties of three samples of the modified stainless steel (referred as the alloy D9) were systematically characterized after neutron irradiation in the Advanced Test Reactor. The samples were irradiated to 5.0, 8.2, and 9.2 displacements per atom at 448, 430, and 683°C, respectively. The evolutions of dislocation loops, cavities, and radiation-induced precipitates were quantitatively studied to reveal their dose and temperature dependencies. Nanohardness and nanoindentation creep tests were conducted at room temperature on the irradiated samples. Unexpected radiation hardening was observed in the highest-temperature-irradiated sample due to the formation of an unknown type of Ni- and Si-rich precipitates whose contributions to the radiation and mechanical performances of the alloy were discussed. We provide the radiation-microstructure-property correlations of alloy D9 with new insights, which can benefit the development and optimization of advanced austenitic alloys for future nuclear applications.
Presentations:
"Ion Irradiation Defects in Austenitic Alloy 709 and Ferritic-Martensitic Steel Grade 92 for Nuclear Applications" Li He, Rigen Mo, Beata Tyburska-Puschel, Kumar Sridharan, Haixuan Xu, Tianyi Chen, Lizhen Tan, MRS Spring 2017 April 17-21, (2017)
NSUF Articles:
U.S. DOE Nuclear Science User Facilities Awards 35 Rapid Turnaround Experiment Research Proposals - Awards total approximately $1.3 million These projects will continue to advance the understanding of irradiation effects in nuclear fuels and materials in support of the mission of the DOE Office of Nuclear Energy. Wednesday, September 20, 2017 - Calls and Awards
RTE 1st Call Awards Announced - Projects total approximately $1.4 million These projects will continue to advance the understanding of irradiation effects in nuclear fuels and materials in support of the mission of the DOE-NE. Friday, February 8, 2019 - Calls and Awards
NSUF awards 28 Rapid Turnaround Experiment proposals - Approximately $1.74M has been awarded. The new call closes June 28. Thursday, June 1, 2023 - Calls and Awards

About Us

The Nuclear Science User Facilities (NSUF) is the U.S. Department of Energy Office of Nuclear Energy's only designated nuclear energy user facility. Through peer-reviewed proposal processes, the NSUF provides researchers access to neutron, ion, and gamma irradiations, post-irradiation examination and beamline capabilities at Idaho National Laboratory and a diverse mix of university, national laboratory and industry partner institutions.

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