@article{zhao_schoell_zheng_cinbiz_frost_an_kaoumi_2021, title={Creep properties of advanced austenitic steel 709 determined through short experiments under in-situ neutron diffraction followed by TEM characterization}, volume={182}, ISSN={["1873-4189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85118186981&partnerID=MN8TOARS}, DOI={10.1016/j.matchar.2021.111519}, abstractNote={In this study, the creep mechanisms at play in Alloy 709 (Fe-20Cr-25Ni) are investigated by performing short-term creep-type tests under in-situ neutron diffraction experiments. Short tests are performed in the temperature range of 500 to 900 °C under constant load with a load ranging from 50 to 150 MPa. The creep exponent and activation energy are determined using the Bird-Mukherjee-Dorn relation and compared to that obtained from conventional longer creep tests from the literature. Scanning transmission electron microscopy (S/TEM) of the post-creep microstructure indicates that interaction of dislocations with precipitates are a dominant mechanism at play. Furthermore, local elemental mapping indicated chemical segregation at grain boundaries and formation of complex precipitates.}, journal={MATERIALS CHARACTERIZATION}, author={Zhao, Yuchen and Schoell, Ryan and Zheng, Ce and Cinbiz, Mahmut N. and Frost, Matthew and An, Ke and Kaoumi, Djamel}, year={2021}, month={Dec} }
 @article{duemmler_zheng_baumier_gentils_kaoumi_2021, title={Helium bubble nucleation and growth in alloy HT9 through the use of in situ TEM: Sequential he-implantation and heavy-ion irradiation versus dual-beam irradiation}, volume={545}, ISSN={["1873-4820"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85095569165&partnerID=MN8TOARS}, DOI={10.1016/j.jnucmat.2020.152641}, abstractNote={The formation of He bubbles in Ferritic/Martensitic steel HT9 is investigated through the use of in situ Transmission Electron Microscopy coupled with He implantation and heavy ion irradiation. Of particular interest is the effect of increasing He appm/dpa ratio on the formation and growth of the bubbles, as well as the effect of the sequential order of ion irradiation i.e. He-pre-implantation followed by heavy-ion irradiation versus true dual-beam irradiation. The role of He is discussed.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Duemmler, Kai and Zheng, Ce and Baumier, Cedric and Gentils, Aurelie and Kaoumi, Djamel}, year={2021}, month={Mar} }
 @article{wang_zheng_kombaiah_tan_sprouster_snead_zinkle_yang_2020, title={Contrasting roles of Laves_Cr2Nb precipitates on the creep properties of novel CuCrNbZr alloys}, volume={779}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2020.139110}, abstractNote={To enhance the creep resistance at elevated temperatures, a new precipitation-strengthened CuCrNbZr alloy has been designed and fabricated to achieve a target microstructure with coarse Laves_Cr2Nb precipitates at grain boundaries and fine Cr-rich precipitates in the matrix. This work systematically studied the creep property of the CuCrNbZr alloy at 500 °C under 90–140 MPa applied stress and compared to that of a reference commercial CuCrZr alloy without Laves_Cr2Nb precipitates. Microstructures before and after creep testing were investigated by optical and transmission electron microscopy. Based on the creep testing and microstructural characterization results, the dominant creep mechanism in both alloys was grain boundary sliding with a threshold stress of ~80 MPa. The CuCrNbZr alloy has higher creep strength and higher creep fracture ductility, and longer creep life than the CuCrZr alloy. The improved creep property in the CuCrNbZr alloy was due to the presence of Laves_Cr2Nb precipitates that efficiently impede the crack propagation.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Wang, Ling and Zheng, Ce and Kombaiah, Boopathy and Tan, Lizhen and Sprouster, David J. and Snead, Lance L. and Zinkle, Steven J. and Yang, Ying}, year={2020}, month={Mar} }
 @article{zheng_kaoumi_2020, title={Dislocation loop evolution in F/M steel T91 under in-situ ion irradiation: Influence of the presence of initial dislocations}, volume={540}, ISSN={["1873-4820"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85087763078&partnerID=MN8TOARS}, DOI={10.1016/j.jnucmat.2020.152363}, abstractNote={Ferritic/Martensitic (F/M) steel T91 was irradiated in-situ to 4 and 10 dpa at 470 °C using 1 MeV Kr2+. The microstructure evolution under irradiation was followed and characterized by in-situ Transmission Electron Microscopy (TEM), in terms of dislocation loop Burgers vector, average size and density as a function of dose. Furthermore, the influence of the presence of dislocations in the pre-irradiated matrix was investigated by comparing the radiation induced defect evolution in grains with and without initial dislocations.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Zheng, Ce and Kaoumi, Djamel}, year={2020}, month={Nov} }
 @article{schoell_frazer_zheng_hosemann_kaoumi_2020, title={In Situ Micropillar Compression Tests of 304 Stainless Steels After Ion Irradiation and Helium Implantation}, volume={72}, ISSN={["1543-1851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85082954591&partnerID=MN8TOARS}, DOI={10.1007/s11837-020-04127-2}, number={7}, journal={JOM}, author={Schoell, Ryan and Frazer, David and Zheng, Ce and Hosemann, Peter and Kaoumi, Djamel}, year={2020}, month={Jul}, pages={2778–2785} }
 @article{zheng_reese_field_liu_marquis_maloy_kaoumi_2020, title={Microstructure response of ferritic/martensitic steel HT9 after neutron irradiation: Effect of temperature}, volume={528}, ISSN={["1873-4820"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073823752&partnerID=MN8TOARS}, DOI={10.1016/j.jnucmat.2019.151845}, abstractNote={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).}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Zheng, Ce and Reese, Elaina R. and Field, Kevin G. and Liu, Tian and Marquis, Emmanuelle A. and Maloy, Stuart A. and Kaoumi, Djamel}, year={2020}, month={Jan} }
 @article{zheng_ke_maloy_kaoumi_2019, title={Correlation of in-situ transmission electron microscopy and microchemistry analysis of radiation-induced precipitation and segregation in ion irradiated advanced ferritic/martensitic steels}, volume={162}, ISSN={["1359-6462"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85058704067&partnerID=MN8TOARS}, DOI={10.1016/j.scriptamat.2018.12.018}, abstractNote={This article presents a novel method combining ion irradiation, in-situ transmission electron microscopy (TEM), and microchemistry analysis before/after irradiation, which allows to examine same microstructural areas throughout ion irradiation. A 12 wt% Cr Ferritic/Martensitic steel (HT9) was irradiated in the TEM to 1.17 × 1020 ions·m−2 at 440 °C using 1 MeV Kr2+ ions, and the in-situ characterization focused on radiation-induced precipitation and segregation. Results of in-situ experiments were compared with those obtained from ex-situ experiments, to showcase how this method helps to better understand precipitation kinetics in the irradiated material examined ex-situ, for which only snapshots are available at limited doses.}, journal={SCRIPTA MATERIALIA}, author={Zheng, Ce and Ke, Jia-Hong and Maloy, Stuart A. and Kaoumi, Djamel}, year={2019}, month={Mar}, pages={460–464} }
 @article{fang_he_ruiz_zheng_wang_li_zhu_2019, title={Influence of annealing parameters on the mechanical properties of heterogeneous lamella structured 5083 aluminum alloy}, volume={9}, ISSN={["2410-3535"]}, DOI={10.22226/2410-3535-2019-4-556-560}, abstractNote={1Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA 2Department of Microsystems — IMS, Faculty of Technology, Natural Sciences and Maritime Sciences, University of South-Eastern Norway, Postboks 235, 3603, Kongsberg, Norway 3Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695, USA 4School of Aeronautics and Astronautics, Sichuan University, Chengdu, 610065, China 5Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, 110819, China 6Nano and Heterogeneous Structural Materials Center, Nanjing University of Science and Technology, Nanjing, 210094, China}, number={4}, journal={LETTERS ON MATERIALS}, author={Fang, X. T. and He, G. Z. and Ruiz, M. and Zheng, C. and Wang, Y. F. and Li, Z. K. and Zhu, Y. T.}, year={2019}, month={Dec}, pages={556–560} }
 @article{zheng_schoell_hosemann_kaoumi_2019, title={Ion irradiation effects on commercial PH 13-8 Mo maraging steel Corrax}, volume={514}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85058006280&partnerID=MN8TOARS}, DOI={10.1016/j.jnucmat.2018.11.041}, abstractNote={The effects of irradiation on the precipitation behavior of commercial PH 13-8 Mo maraging steel a.k.a. Corrax are investigated through in-situ ion irradiation. Samples of the alloy in its solution annealed state are irradiated up to 10 dpa at 573 and 773 K using 1 MeV Kr ions, in-situ in a transmission electron microscope in order to probe irradiation effects on the precipitation usually observed in this alloy under thermal aging. Indeed, the alloy is known to develop a relatively fine distribution of precipitates during thermal aging which gives the martensitic alloy its strength. The effects of irradiation are substantiated by comparing with the same material thermally aged at 773 and 873 K for similar amounts of experimental time. Both radiation and thermal aging induced segregation and precipitation are characterized using analytical transmission electron microscopy (TEM) techniques. The diffusion coefficients under irradiation are estimated using the point defect balance equations based on Rate Theory and then compared with the thermal diffusion coefficients, demonstrating the accelerated precipitation of β-phase and Laves-phase in the irradiation case at relatively lower temperature is attributed to the radiation-enhanced diffusion. In addition, a numerical model based on classical precipitate nucleation and growth theories is introduced and shows a relatively good agreement with the experimental results in terms of precipitate density. This study serves to generate baseline data on ion irradiation effects on Corrax to learn how this steel responds to irradiation.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Zheng, Ce and Schoell, Ryan and Hosemann, Peter and Kaoumi, Djamel}, year={2019}, pages={255–265} }
 @article{zheng_reese_field_marquis_maloy_kaoumi_2019, title={Microstructure response of ferritic/martensitic steel HT9 after neutron irradiation: effect of dose}, volume={523}, ISSN={["1873-4820"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85067602813&partnerID=MN8TOARS}, DOI={10.1016/j.jnucmat.2019.06.019}, abstractNote={A ferritic/martensitic steel, HT9, was irradiated in the BOR-60 reactor to ∼17.1 and ∼35.1 displacements per atom (dpa) at 650 ± 23 K (377 ± 23 °C). Irradiated samples were comprehensively characterized using analytical scanning/transmission electron microscopy and atom probe tomography, with emphasis on the role of irradiation dose on the microstructure evolution. Radiation-induced Mn/Ni/Si-rich (G-phase) and radiation-enhanced Cr-rich (αʹ) precipitates were observed within the martensitic laths at all doses. In addition, the G-phase was also observed to precipitate heterogeneously at various defect sinks. The number density for these second-phase precipitates decreases while the size increases with increasing dose, resulting in an increase of the volume fraction. Both a <100> and a/2 <111> type loops were observed with the a <100> type being the predominant type at both doses. The proportion of a <100> loops is consistent with that previously observed in HT9 ion irradiated to similar doses at ∼693–743 K (∼420-470 °C). Only small cavities (diameter < 2 nm) were observed at ∼17.1 dpa whereas both small and large cavities were observed at ∼35.1 dpa, resulting in a bi-modal cavity size distribution at this dose. Alloying elements, Ni and Si, were observed to segregate to the cavity surface, forming Ni/Si-rich shells around the cavities. The swelling at ∼17.1 dpa is evaluated at ∼0.02% while the swelling at ∼35.1 dpa is found to be ∼0.07% with variations from grain to grain. attributed to the spatial variation of the density of large cavities (in different grains). The swelling data obtained in this study was compared with the neutron data of F/M steels available in the literature.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Zheng, Ce and Reese, Elaina R. and Field, Kevin G. and Marquis, Emmanuelle and Maloy, Stuart A. and Kaoumi, Djamel}, year={2019}, month={Sep}, pages={421–433} }
 @article{zheng_auger_moody_kaoumi_2017, title={Radiation induced segregation and precipitation behavior in self-ion irradiated Ferritic/Martensitic HT9 steel}, volume={491}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85019131192&partnerID=MN8TOARS}, DOI={10.1016/j.jnucmat.2017.04.040}, abstractNote={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.}, journal={Journal of Nuclear Materials}, author={Zheng, C. and Auger, M. A. and Moody, M. P. and Kaoumi, Djamel}, year={2017}, pages={162–176} }
 @article{zheng_kaoumi_2017, title={Radiation-induced swelling and radiation-induced segregation & precipitation in dual beam irradiated Ferritic/Martensitic HT9 steel}, volume={134}, ISSN={["1873-4189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85032004953&partnerID=MN8TOARS}, DOI={10.1016/j.matchar.2017.10.019}, abstractNote={Ferritic/Martensitic HT9 steel was irradiated at 432 °C to 16.6 displacements per atom (dpa) (at the depth of 600 nm) using a defocused beam of 5 MeV Fe++ ions, while co-implanted with 3.22 appm He at the same depth. The helium concentration profile was designed so to follow the damage curve with a 0.22 appm He/dpa ratio at the depth from 300 to 1000 nm in the material. The depth-dependence of the cavity size and number density were characterized by both transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) imaging methods. A comparison between the two techniques was done showing good agreement. Cavity number density and the resulting swelling were found to be suppressed by the injected interstitial effect in the vicinity of the ion induced damage peak. The region between 300 and 750 nm depth which excludes the injected interstitial effect was thus proposed for improved cavity swelling analysis. The swelling ratio in this region was found to be ~(0.86–1.02) × 10− 2%/dpa. In addition, ChemiSTEM characterization revealed radiation-induced segregation occurring throughout the irradiated region and precipitation of G-phase particles. Segregation of Ni to cavity surfaces was also observed and its possible synergistic influence on swelling was discussed.}, journal={MATERIALS CHARACTERIZATION}, author={Zheng, C. and Kaoumi, D.}, year={2017}, month={Dec}, pages={152–162} }
 @article{zheng_gentils_ribis_borodin_descoins_mangelinck_dalle_arnal_delauche_2017, title={Thermal annealing behavior of nano-size metal-oxide particles synthesized by ion implantation in Fe-Cr alloy}, volume={121}, ISSN={["1089-7550"]}, DOI={10.1063/1.4982756}, abstractNote={Oxide dispersion strengthened (ODS) steels are promising structural materials for the next generation nuclear reactors, as well as fusion facilities. The detailed understanding of the mechanisms involved in the precipitation of nano-oxides during ODS steel production would strongly contribute to the improvement of the mechanical properties and the optimization of manufacturing of ODS steels, with a potentially strong economic impact for their industrialization. A useful tool for the experimental study of nano-oxide precipitation is ion implantation, a technique that is widely used to synthesize precipitate nanostructures in well-controlled conditions. Earlier, we have demonstrated the feasibility of synthesizing aluminum-oxide particles in the high purity Fe-10Cr alloy by consecutive implantation with Al and O ions at room temperature. This paper describes the effects of high-temperature annealing after the ion implantation stage on the development of the aluminum based oxide nanoparticle system. Using transmission electron microscopy and atom probe tomography experiments, we demonstrate that post-implantation heat treatment induces the growth of the nano-sized oxides in the implanted region and nucleation of new oxide precipitates behind the implantation zone as a result of the diffusion driven broadening of implant profiles. A tentative scenario for the development of metal-oxide nano-particles at both ion implantation and heat treatment stages is suggested based on the experimental observations.}, number={17}, journal={JOURNAL OF APPLIED PHYSICS}, author={Zheng, C. and Gentils, A. and Ribis, J. and Borodin, V. A. and Descoins, M. and Mangelinck, D. and Dalle, F. and Arnal, B. and Delauche, L.}, year={2017}, month={May} }