Cheng Sun

"Effect of laser welding on deformation mechanisms in irradiated austenitic stainless steel" Janelle Wharry, Keyou Mao, Cheng Sun, Xiang Liu, Haozheng Qu, Aaron French, Paula Freyer, Frank Garner, Lin Shao, Journal of Nuclear Materials Vol. 528 2020 151878 Link
Deformation mechanism of a laser weld on neutron irradiated AISI 304L stainless steel was studied by in-situ microcompression test at room temperature. The deformation-induced austenite-to-martensite phase transformation occurs in {101}-oriented grains in the irradiated base metal, while deformation twinning prevails in {101}-oriented grains in the weld heat affected zone (HAZ). A high number density of irradiation-induced voids in the base metal provides sufficient nucleation sites for the austenite-to-martensite phase transformation under compression at room temperature. A deformation map is established to predict critical twinning stress for face-centered-cubic (fcc) metals and alloys. Our results show that irradiation-induced voids can tailor the deformation mechanisms of austenitic stainless steel.
"Enhanced radiation tolerance of ultrafine grained Fe–Cr–Ni alloy" Yingtao Liu, Lin Shao, Cheng Sun, Journal of Nuclear Materials Vol. 420 2012 235 Link
The evolutions of microstructure and mechanical properties of Fe–14Cr–16Ni (wt.%) alloy subjected to Helium ion irradiations were investigated. Equal channel angular pressing (ECAP) process was used to significantly reduce the average grain size from 700 lm to 400 nm. At a peak fluence level of 5.5 displacement per atom (dpa), helium bubbles, 0.5–2 nm in diameter, were observed in both coarse-grained (CG) and ultrafine grained (UFG) alloy. The density of He bubbles, dislocation loops, as well as radiation hardening were reduced in the UFG Fe–Cr–Ni alloy comparing to those in its CG counterpart. The results imply that radiation tolerance in bulk metals can be effectively enhanced by refinement of microstructures.
"Formation of tetragonal gas bubble superlattice in bulk molybdenum under helium ion implantation" Cheng Sun, David Sprouster, Khalid Hattar, Lynne Ecker, Lingfeng He, Y. Gao, Yipeng Gao, Yongfeng Zhang, Jian Gan, Scripta Materialia Vol. 149 2018 26-30 Link
We report the formation of tetragonal gas bubble superlattice in bulk molybdenum under helium ion implantation at 573 K. The transmission electron microscopy study shows that the helium bubble lattice constant measured from the in-plane d-spacing is ~4.5 nm, while it is ~3.9 nm from the out-of-plane measurement. The results of synchrotron-based small-angle x-ray scattering agree well with the transmission electron microscopy results in terms of the measurement of bubble lattice constant and bubble size. The coupling of transmission electron microscopy and synchrotron high-energy X-ray scattering provides an effective approach to study defect superlattices in irradiated materials.
"Grain orientation dependence of nanoindentation and deformation-induced martensitic phase transformation in neutron irradiated AISI 304L stainless steel" Keyou Mao, Cheng Sun, Yina Huang, Ching-Heng Shiau, Frank Garner, Paula Freyer, Janelle Wharry, Materialia Vol. 5 2019 100208 Link
"Grain refinement mechanisms and strength-hardness correlation of ultra-fine grained grade 91 steel processed by equal channel angular extrusion" Miao Song, Cheng Sun, Youxing Chen, Zhongxia Shang, Jin Li, Zhe Fan, Karl Hartwig, Xinghang Zhang, International Journal of Pressure Vessels and Piping Vol. 172 [unknown] 212-219 Link
"In situ neutron diffraction study on temperature dependent deformation mechanisms of ultrafine grained austenitic Fe-14Cr-16Ni alloy" Bjorn Clausen, Stuart Maloy, Cheng Sun, Kaiyuan Yu, International Journal of Plasticity Vol. 53 2014 125-134 Link
"In situ studies of Kr ion irradiation response of Fe/Y2O3 nanolayers" Youxing Chen, Liang Jiao, Cheng Sun, Miao Song, Kaiyuan Yu, Yue Liu, Meimei Li, Haiyan Wang, Xinghang Zhang, Journal of Nuclear Materials Vol. 452 2014 321 Link
"In situ study of defect migration kinetics in nanoporous Ag with enhanced radiation tolerance" Cheng Sun, Youxing Chen, Yongqiang Wang, Meimei Li, Haiyan Wang, Xinghang Zhang, Scientific Report Vol. 4 2014 Link
"Influence of injected interstitials on the void swelling in two structural variants of 304L stainless steel induced by self-ion irradiation at 500 °C" Cheng Sun, Frank Garner, Lin Shao, Xinghang Zhang, Stuart Maloy, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Vol. 409 2017 323-327 Link
"Laser weld-induced formation of amorphous Mn-Si precipitate in 304 stainless steel" Janelle Wharry, Keyou Mao, Yaqiao Wu, Cheng Sun, Emmanuel Perez, Materialia Vol. 3 2018 174-177
"Measurement of grain boundary strength of Inconel X-750 superalloy using in-situ micro-tensile testing techniques in FIB/SEM system" Yachun Wang, Xiang Liu, Daniel Murray, Fei Teng, Wen Jiang, Mukesh Bachhav, Laura Hawkins, Emmanuel Perez, Cheng Sun, Xianming Bai, Jie Lian, Colin Judge, John Jackson, Robert Carter, Lingfeng He, Materials Science & Engineering Vol. 849 2022
"Microstructure and microchemistry of laser welds of irradiated austenitic steels" Keyou Mao, Aaron French, Xiang Liu, Lucille Giannuzzi, Cheng Sun, Megha Dubey, Paula Freyer, Jonathan Tatman, Frank Garner, Lin Shao, Janelle Wharry, Materials and Design Vol. 206 2021 Link
"Microstructure of laser weld repairs of irradiated austenitic steels" Janelle Wharry, Keyou Mao, Aaron French, Xiang Liu, Yaqiao Wu, Cheng Sun, Paula Freyer, Jonathan Tatman, Lucille Giannuzzi, Frank Garner, Lin Shao, Materials & Design Vol. 206 2021 109764 Link
"Nanocluster Evolution in D9 Austenitic Steel under Neutron and Proton Irradiation" Janelle Wharry, Mukesh Bachhav, Cheng Sun, Amrita Sen, Suraj Venkateshwaran Mullurkara, Akshara Bejawada, Materials Vol. 16 2023 4852 Link
Austenitic stainless steel D9 is a candidate for Generation IV nuclear reactor structural materials due to its enhanced irradiation tolerance and high-temperature creep strength compared to conventional 300-series stainless steels. But, like other austenitic steels, D9 is susceptible to irradiation- induced clustering of Ni and Si, the mechanism for which is not well understood. This study utilizes atom probe tomography (APT) to characterize the chemistry and morphology of Ni–Si nanoclusters in D9 following neutron or proton irradiation to doses ranging from 5–9 displacements per atom (dpa) and temperatures ranging from 430–683 ºC. Nanoclusters form only after neutron irradiation and exhibit classical coarsening with increasing dose and temperature. The nanoclusters have Ni3Si stoichiometry in a Ni core–Si shell structure. This core–shell structure provides insight into a potentially unique nucleation and growth mechanism—nanocluster cores may nucleate through local, spinodal-like compositional fluctuations in Ni, with subsequent growth driven by rapid Si diffusion. This study underscores how APT can shed light on an unusual irradiation-induced nanocluster nucleation mechanism active in the ubiquitous class of austenitic stainless steels.
"Orientation-selected micro-pillar compression of additively manufactured 316L stainless steels: Comparison of as-manufactured, annealed, and proton-irradiated variants" Ching-Heng Shiau, Cheng Sun, Michael McMurtrey, Frank Garner, Lin Shao, JNM Vol. 566 2022 Link
"Probing the Damage Recovery Mechanism in Irradiated Stainless Steels Using In-Situ Microcantilever Bending Test" Keyou Mao, Hao Wang, Haozheng Qu, Kayla Yano, Philip Edmondson, Cheng Sun, Janelle Wharry, Frontiers in Materials Vol. 2022 Link
"Radiation damage in nanostructured materials" Xinghang Zhang, Khalid Hattar, Youxing Chen, Lin Shao, Jin Li, Cheng Sun, Kaiyuan Yu, Nan Li, Mitra Taheri, Haiyan Wang, Progress in Materials Science Vol. 96 2018 217-321 Link
"Removal of stacking-fault tetrahedra by twin boundaries in nanotwinned metals" Kaiyuan Yu, Cheng Sun, Yue Liu, Haiyan Wang, Mark Kirk, Meimei Li, Xinghang Zhang, Nature Communications Vol. 4 2013 Link
"Resilient ZnO nanowires in an irradiation enviroment: an in situ study" Cheng Sun, Jin Li, Youxing Chen, Mark Kirk, Meimei Li, Stuart Maloy, Haiyan Wang, Xinghang Zhang, Acta Materialia Vol. 95 2015 156 Link
"Role of cavities on deformation-induced martensitic transformation pathways in a laser-welded, neutron irradiated austenitic stainless steel" Janelle Wharry, Keyou Mao, Cheng Sun, Ching-Heng Shiau, Kayla Yano, Paula Freyer, Anter EL-AZAB, Frank Garner, Aaron French, Lin Shao, Scripta Materialia Vol. 178 2020 1-6 Link
The role of cavities on deformation-induced martensitic phase transformations is studied in a laser-welded and neutron irradiated austenitic stainless steel. Orientation dependent nanoindentation experiments are performed in the base metal and the weld heat affected zone (HAZ) at room temperature. Transmission electron microscopy study of deformed microstructures indicates indentation-induced α’-martensite forms in the base metal, whereas α’- and ε-martensite arise in the HAZ. The different pathway of martensite phase transformation is attributed to the laser weld-induced annealing of cavities. Our results suggest that deformation-induced martensitic phase transformation of austenitic stainless steel is correlated to neutron irradiated cavity structures.
"Superior radiation-resistant nanoengineered austenitic 304L stainless steel for applications in extreme radiation environments" Cheng Sun, Lin Shao, Steven Zinkle, Todd Allen, Haiyan Wang, Xinghang Zhang, Scientific Reports Vol. 5 2015 Link
"Thermal stability of helium bubble superlattice in Mo under TEM in-situ heating" Jian Gan, Cheng Sun, Lingfeng He, Yongfeng Zhang, Chao Jiang, Yipeng Gao, Journal of Nuclear Materials Vol. 505 2018 207-211 Link
Although the temperature window of helium ion irradiation for gas bubble superlattice (GBS) formation was found to be in the range of approximately 0.15–0.35 melting point in literature, the thermal stability of He GBS has not been fully investigated. This work reports the experiment using an in-situ heating holder in a transmission electron microscope (TEM). A 3.0 mm TEM disc sample of Mo (99.95% pure) was irradiated with 40 keV He ions at 300 °C to a fluence of 1.0E+17 ions/cm2, corresponding to a peak He concentration of approximately 10 at.%, in order to introduce He GBS. In-situ heating was conducted with a ramp rate of ∼25 °C/min, hold time of ∼30 min, and temperature step of ∼100 °C up to 850 °C (0.39Tm homologous temperature). The result shows good thermal stability of He GBS in Mo with no noticeable change on GBS lattice constant and ordering. The implication of this unique and stable ordered microstructure on mechanistic understanding of GBS and its advanced application are discussed.
"Microstructural and micromechanical characterization of laser weld repairs on neutron irradiated 304 stainless steel" Keyou Mao, Paula Freyer, Cheng Sun, Frank Garner, Janelle Wharry, NUMAT 2018 October 15-18, (2018)
NSUF Articles:
U.S. DOE Nuclear Science User Facilities Awards 30 Rapid Turnaround Experiment Research Proposals - Awards total nearly $1.2 million The U.S. Department of Energy (DOE) Nuclear Science User Facilities (NSUF) has selected 30 new Rapid Turnaround Experiment (RTE) projects, totaling up to 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. Wednesday, April 26, 2017 - Calls and Awards
NSUF Research Collaborations

Alleviating irradiation-induced precipitation in a Fe-21Cr-5Al alloy via nanostructuring. - FY 2019 RTE 2nd Call, #1761

Creation of gas bubble superlattice in tungsten and tungsten alloys - FY 2020 RTE 1st Call, #2984

Determination of spatial and chemical relationship of hydrogen and helium in 316 SS PWR flux thimble tube at 76 dpa for extrapolation into beyond-40-year operation - FY 2019 RTE 3rd Call, #2857

Effect of laser weld repairs on deformation mechanisms of neutron irradiated austenitic steels - FY 2019 RTE 1st Call, #1619

Evolution of Dispersoid in Austenitic Fe-Cr-Ni Oxide Dispersion Strengthened Alloy in Ion Irradiation - FY 2023 RTE 1st Call, #4508

Gas bubble superlattice formation in metals at cryogenic temperature and in ceramics at high temperature New Proposal - FY 2023 RTE 2nd Call, #4697

Investigation of gas bubble behavior in metals using in-situ Ne, Ar and Kr ion irradiation - FY 2018 RTE 1st Call, #1213

Investigation of gas bubble behavior under ion irradiation - FY 2017 RTE 2nd Call, #912

Irradiation Damage in (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C High-Entropy Ceramics - FY 2018 RTE 3rd Call, #1589

Local Deformation Mechanism of Neutron-Irradiated NF709 Austenitic Stainless Steel - FY 2019 RTE 1st Call, #1652

Microstructure and microchemical characterization of neutron and proton irradiated Alloy D9 using APT and TEM - FY 2017 RTE 3rd Call, #1081

Post-irradiation observation following high-rate self-ion irradiation of previously neutron-irradiated 304 stainless steel - FY 2017 RTE 3rd Call, #1055

Preliminary testing of additively manufactured UO2 - FY 2023 RTE 3rd Call, #4778