Djamel Kaoumi

Profile Information
Name
Professor Djamel Kaoumi
Institution
North Carolina State University
Position
Associate Professor
Affiliation
North Carolina State University
h-Index
ORCID
0000-0001-7055-0444
Biography

Dr. Kaoumi’s research interests revolve around developing a mechanistic understanding of microstructure property relationships in nuclear materials, with an emphasis on microstructure evolution under harsh environment (i.e. irradiation, high temperature, and mechanical stress) and how it can impact the macroscopic properties and performance. Understanding the basic mechanisms of degradation of materials at the nanostructure level is necessary for the development of predictive models of the materials performance and for the design and development of better materials. Materials of interest include advanced alloys for structural and cladding applications in advanced nuclear systems (e.g. Austenitic steels , Advanced Ferritic/Martensitic Steels, Oxide-Dispersion-Strengthened (ODS) Steels), High-temperature Ni-based alloys, Zirconium alloys and nanocrystalline metallic systems. Characterization techniques of predilection include both in-situ and ex-situ techniques e.g. In-situ irradiation in TEM (over 15 years of experience), In-situ straining in a TEM, chemi-STEM, SEM, XRD, Synchrotron XRD.

Expertise
Austenitic stainless steels, Cladding, Ferritic Martensitic Steels, In Situ Electron Microscopy, In Situ Ion Irradiation, Ion-Irradiation, Microstructural Evolution, Neutron Irradiation, ODS, Post-Irradiation Examination, X-Ray Computed Tomography
Publications:
"Characterization of microstructure and property evolution in advanced cladding and duct: Materials exposed to high dose and elevated temperature" Todd Allen, Zhijie Jiao, Djamel Kaoumi, Janelle Wharry, cem topbasi, Aaron Kohnert, Leland Barnard, Alicia Certain, Kevin Field, Gary Was, Dane Morgan, Arthur Motta, Brian Wirth, Yong Yang, Journal of Materials Research Vol. 30 2015 1246-1274 Link
Designing materials for performance in high-radiation fields can be accelerated through a carefully chosen combination of advanced multiscale modeling paired with appropriate experimental validation. The studies reported in this work, the combined efforts of six universities working together as the Consortium on Cladding and Structural Materials, use that approach to focus on improving the scientific basis for the response of ferritic–martensitic steels to irradiation. A combination of modern modeling techniques with controlled experimentation has specifically focused on improving the understanding of radiation-induced segregation, precipitate formation and growth under radiation, the stability of oxide nanoclusters, and the development of dislocation networks under radiation. Experimental studies use both model and commercial alloys, irradiated with both ion beams and neutrons. Transmission electron microscopy and atom probe are combined with both first-principles and rate theory approaches to advance the understanding of ferritic–martensitic steels.
"Correlation of in-situ transmission electron microscopy and microchemistry analysis of radiation-induced precipitation and segregation in ion-irradiated advanced ferritic/martensitic steels" Ce Zheng, Stuart Maloy, Djamel Kaoumi, Scripta Materialia Vol. 162 2019 460-464 Link
"Deformation induced Martensitic transformation in 304 Austenitic stainless steel: In-situ vs. Ex-situ transmission electron microscopy characterization" Djamel Kaoumi, Junliang Liu, Materials Science and Engineering:A Vol. 715 2018 73-82 Link
304 stainless steel is known to be metastable as the austenite phase can transform into martensite under deformation. In this work, both ex-situ and in-situ transmission electron microscopy (TEM) characterization were used to investigate the mechanisms of the deformation-induced transformation at room temperature. The ex-situ tensile tests were conducted at a strain rate of 10-3 s-1 until rupture, followed by TEM and X-Ray Diffraction (XRD). Samples were also interrupted at strains of 7%, 18%, and 30% with the goal of investigating the intermediate microstructure. In addition, tensile tests were conducted in-situ in a TEM at 25 °C using a special straining-stage with the goal of capturing the nucleation and growth of the martensitic phase as it develops under deformation. The formation of stacking faults and the subsequent formation of e-martensite (hcp) through their overlapping/bundling was captured in-situ, confirming the role played by Stacking Faults (SFs) as intermediate step during the transformation from ?-austenite to e-martensite. Direct transformation of ?-austenite (fcc) to a’-martensite (bcc) was also captured upon straining and characterized. Such unique in-situ observations showcase how in-situ straining in a TEM, as a small scale tensile technique, is a powerful technique to visualize and investigate the mechanisms of deformation induced phase transformations.
"Effect of dose on irradiation-induced loop density and Burgers vector in ion-irradiated ferritic/ martensitic steel HT9" Ce Zheng, Stuart Maloy, Djamel Kaoumi, Philosophical Magazine Vol. 98 2018 2440-2456 Link
TEM samples of F/M steel HT9 were irradiated to 20 dpa at 420°C, 440°C and 470°C in a TEM with 1 MeV Kr ions so that the microstructure evolution could be followed in situ and characterized as a function of dose. Dynamic observations of irradiation-induced defect formation and evolution were done at different temperatures. The irradiation-induced loops were characterized in terms of their Burgers vector, size and density as a function of dose and similar observations and trends were found at the three temperatures: (i) both a/2 <111> and a <100> loops are observed; (ii) in the early stage of irradiation, the density of irradiation-induced loops increases with dose (0-4 dpa) and then decreases at higher doses (above 4 dpa), (iii) the dislocation line density shows an inverse trend to the loop density with increasing dose: in the early stages of irradiation the pre-existing dislocation lines are lost by climb to the surfaces while at higher doses (above 4 dpa), the build-up of new dislocation networks is observed along with the loss of the radiation-induced dislocation loops to dislocation networks; (iv) at higher doses, the decrease of number of loops affects more the a/2 <111> loop population; the possible loss mechanisms of the a/2 <111> loops are discussed. Also, the ratio of a <100> to a/2 <111> loops is found to be similar to cases of bulk irradiation of the same alloy using 5 MeV Fe2+ions to similar doses of 20 dpa at similar temperatures.
"Ion irradiation effects on commercial PH 13-8 Mo maraging steel Corrax" Ce Zheng, Ryan Schoell, Peter Hosemann, Djamel Kaoumi, Journal of Nuclear Materials Vol. 514 2019 255-265 Link
"Microstructural and nanomechanical characterization of in-situ He implanted and irradiated fcc materials" David Frazer, Peter Hosemann, Djamel Kaoumi, Ce Zheng, Microscopy & Microanalysis Vol. 23 (Suppl 1) 2017 756-757 Link
"Microstructure characterization of ion-irradiated Ferritic/Martensitic HT9 steel" Djamel Kaoumi, Ce Zheng, Microscopy & Microanalysis Vol. 23 2017 Link
"Microstructure response of ferritic/martensitic steel HT9 after neutron irradiation: Effect of temperature" Ce Zheng, Elaina Reese, Kevin Field, Tian Liu, Emmanuelle Marquis, Stuart Maloy, Djamel Kaoumi, Journal of Nuclear Materials Vol. 528 2019 Link
The ferritic/martensitic steel HT9 was irradiated in the BOR-60 reactor at 650, 690 and 730 K (377, 417 and 457 °C) to doses between ∼14.6–18.6 displacements per atom (dpa). Irradiated samples were comprehensively characterized using analytical scanning/transmission electron microscopy and atom probe tomography, with emphasis on the influence of irradiation temperature on microstructure evolution. Mn/Ni/Si-rich (G-phase) and Cr-rich (αʹ) precipitates were observed within martensitic laths and at various defect sinks at 650 and 690 K (377 and 417 °C). For both G-phase and αʹ precipitates, the number density decreased while the size increased with increasing temperature. At 730 K (457 °C), within martensitic laths, a very low density of large G-phase precipitates nucleating presumably on dislocation lines was observed. No αʹ precipitates were observed at this temperature. Both a <100> and a/2 <111> type dislocation loops were observed, with the a <100> type being the predominant type at 650 and 690 K (377 and 417 °C). On the contrary, very few dislocation loops were observed at 730 K (457 °C), and the microstructure was dominated by a/2 <111> type dislocation lines (i.e., dislocation network) at this temperature. Small cavities (diameter < 2 nm) were observed at all three temperatures, whereas large cavities (diameter > 2 nm) were observed only at 690 K (417 °C), resulting in a bimodal cavity size distribution at 690 K (417 °C) and a unimodal size distribution at 650 and 730 K (377 and 457 °C). The highest swelling (%) was observed at 690 K (417 °C), indicating that the peak of swelling happens between 650 and 730 K (377 and 457 °C).
"Radiation induced segregation and precipitation behavior in self-ion irradiated Ferritic/Martensitic HT9 steel" Maria A Auger, Djamel Kaoumi, Ce Zheng, Michael Moody, Journal of Nuclear Materials Vol. 491 2017 162-176 Link
In this study, Ferritic/Martensitic (F/M) HT9 steel was irradiated to 20 displacements per atom (dpa) at 600 nm depth at 420 and 440 °C, and to 1, 10 and 20 dpa at 600 nm depth at 470 °C using 5 MeV Fe++ ions. The characterization was conducted using ChemiSTEM and Atom Probe Tomography (APT), with a focus on radiation induced segregation and precipitation. Ni and/or Si segregation at defect sinks (grain boundaries, dislocation lines, carbide/matrix interfaces) together with Ni, Si, Mn rich G-phase precipitation were observed in self-ion irradiated HT9 except in very low dose case (1 dpa at 470 °C). Some G-phase precipitates were found to nucleate heterogeneously at defect sinks where Ni and/or Si segregated. In contrast to what was previously reported in the literature for neutron irradiated HT9, no Cr-rich α′ phase, χ-phases, η phase and voids were found in self-ion irradiated HT9. The difference of observed microstructures is probably due to the difference of irradiation dose rate between ion irradiation and neutron irradiation. In addition, the average size and number density of G-phase precipitates were found to be sensitive to both irradiation temperature and dose. With the same irradiation dose, the average size of G-phase increased whereas the number density decreased with increasing irradiation temperature. Within the same irradiation temperature, the average size increased with increasing irradiation dose.
"Use of in-situ TEM to characterize the deformation-induced Martensitic transformation in 304 stainless steel at cryogenic temperature" Djamel Kaoumi, Junliang Liu, Materials Characterization Vol. 136 2018 331-336 Link
Tensile tests are conducted in-situ in a TEM at cryogenic temperatures (from - 100 °C to 0 °C) using a cooling TEM straining-stage with the goal of capturing the growth of the martensitic phase as it develops under stress in the material. The in-situ technique is used to explore the mechanism of deformation induced martensitic transformation in 304 and 304L austenitic stainless steels. The formation of stacking faults is captured, as well as the subsequent formation of e-martensite, confirming the role played by Stacking faults (SFs) as intermediate step during the transformation from ?-austenite to e-martensite. In addition, direct transformation from ?-austenite to a'-martensite is captured (i) upon straining at a fixed temperature and (ii) upon cooling after pulling on the sample, indicating how straining and temperature are both effective on the transformation.
Presentations:
"Combined use of in-situ and ex-situ TEM to characterize ion irradiation induced dislocation loops in F/M steels" Djamel Kaoumi, Ce Zheng, E-MRS 2018 June 18-22, (2018)
"Dose effect on the irradiation induced loop density & Burgers vector in ion-irradiated alloy T91 irradiated in-situ in a TEM" Djamel Kaoumi, Ce Zheng, TMS 2018 March 11-15, (2018)
"Dose effect on the irradiation induced loop density and Burgers vector in ion-irradiated ferritic/martensitic steel HT9 through in-situ TEM," Djamel Kaoumi, Ce Zheng, MMM 2018 October 28-2, (2018)
"In-situ ion irradiation induced microstructure evolution in ferritic/martensitic steel HT9" Djamel Kaoumi, Ce Zheng, Microscopy and Microanalysis meeting 2017 August 1-4, (2017)
"In-situ ion irradiation induced microstructure evolution in Ferritic/Martensitic steel T91, poster presentation" Djamel Kaoumi, Ce Zheng, TMS-2017 conference February 26-2, (2017)
"Plasticity studies using in-situ straining TEM experiments: deformation-induced martensitic transformation and dislocation dynamics in steels" Djamel Kaoumi, 21st International Symposium on Plasticity January 3-9, (2017)
"Use of In-Situ TEM to study the Dose Effect on the Irradiation Induced Loop Density and Burgers Vector in an Ion-Irradiated F/M Steel for Nuclear Applications" Djamel Kaoumi, Ce Zheng, WOTWISI-5 April 11-13, (2018)
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
DOE Awards 33 Rapid Turnaround Experiment Research Proposals - Projects total approximately $1.2 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. Monday, June 18, 2018 - Calls and Awards
RTE 2nd Call Awards Announced - Projects total approximately $1.6 million These project awards went to principal investigators from 26 U.S. universities, eight national laboratories, two British universities, and one Canadian laboratory. Tuesday, May 14, 2019 - Calls and Awards
DOE Awards Eight CINR NSUF Projects - Projects include $3M in access grants and R&D funding Monday, July 6, 2020 - Calls and Awards
2020 NSUF Annual Review - Presentations The 2020 NSUF Annual Review presentations are now available online Tuesday, December 15, 2020 - DOE, Annual Review, Presentations