Yiren Chen

"In-situ high-energy X-ray characterization of neutron irradiated HT-UPS stainless steel under tensile deformation" Chi Xu, Xuan Zhang, Yiren Chen, Meimei Li, Jun-Sang Park, Peter Kenesei, Jason Almer, Yong Yang, Acta Materialia Vol. 156 2018 330-341 Link
The tensile deformation behavior of a high-temperature, ultrafine-precipitate strengthened (HT-UPS) stainless steel was characterized in-situ with high-energy X-ray diffraction at 20 and 400?°C. The HT-UPS samples were neutron irradiated to 3 dpa at 400?°C. Significant irradiation hardening and ductility loss were observed at both temperatures. Lattice strain evolutions of the irradiated samples showed a strong linear response up to near the onset of the macroscopic yield, in contrast to the unirradiated HT-UPS which showed a pronounced non-linear behavior well below the macroscopic yield. While the room-temperature diffraction elastic moduli in the longitudinal direction increased after irradiation, the 400?°C moduli were similar before and after irradiation. The evolution of the {200} lattice strain parallel to the loading axis () showed unique characteristics: in the plastic regime, the evolution of after yield is temperature-dependent in the unirradiated specimens but temperature-independent in the irradiated specimens; and the value of at the yield is an irradiation-sensitive, temperature-independent parameter. The evolution of corresponds well with the dislocation density evolution, and is an effective probe of the deformation-induced long-range internal stresses in the HT-UPS steel.
"Irradiation effects on Al0. 3CoCrFeNi and CoCrMnFeNi high-entropy alloys, and 316H stainless steel at 500° C" Wei-Ying Chen, Xiang Liu, Yiren Chen, Journal of Nuclear Materials Vol. 539 2020
To evaluate the potential of high entropy alloys (HEAs) for nuclear applications, two HEAs, Al0.3CoCrFeNi and CoCrFeMnNi, and a conventional Type 316H stainless steel (SS) were irradiated with 1 MeV krypton ions at 500 °C up to 1 dpa, and examined in-situ with a transmission electron microscope (TEM). After irradiation, a high density of ordered L12 nanoparticles was observed in Al0.3CoCrFeNi. In contrast, no phase transformation was observed in CoCrFeMnNi and 316H SS. In the thin foil regions of TEM samples, stacking-fault tetrahedra were observed in the HEAs. In the thick foil regions, interstitial dislocation loops were observed for all alloys, and the areal loop density increased linearly with foil thickness. The Al0.3CoCrFeNi had the largest loop size (the lowest density), followed by the CoCrFeMnNi and then the 316H SS. The higher loop nucleation rate in the 316H SS was attributed to carbon content. The degree of irradiation hardening was slightly lower for the HEAs than for the 316H SS, which is a promising sign for the nuclear application of HEAs at high temperatures.
"Irradiation response of delta ferrite in as-cast and thermally aged cast stainless steel" Todd Allen, Yiren Chen, Zhangbo Li, Wei-Yang Lo, Janne Pakarinen, Yaqiao Wu, Yong Yang, Journal of Nuclear Materials Vol. 466 2015 201-207 Link
To enable the life extension of Light Water Reactors (LWRs) beyond 60 years, it is critical to gain adequate knowledge for making conclusive predictions to assure the integrity of duplex stainless steel reactor components, e.g. primary pressure boundary and reactor vessel internal. Microstructural changes in the ferrite of thermally aged, neutron irradiated only, and neutron irradiated after being thermally aged cast austenitic stainless steels (CASS) were investigated using atom probe tomography. The thermal aging was performed at 400 °C for 10,000 h and the irradiation was conducted in the Halden reactor at ~315 °C to 0.08 dpa (5.6 × 1019 n/cm2, E > 1 MeV). Low dose neutron irradiation at a dose rate of 5 × 10-9 dpa/s was found to induce spinodal decomposition in the ferrite of as-cast microstructure, and further to enhance the spinodal decomposition in the thermally aged cast alloys. Regarding the G-phase precipitates, the neutron irradiation dramatically increases the precipitate size, and alters the composition of the precipitates with increased, Mn, Ni, Si and Mo and reduced Fe and Cr contents. The results have shown that low dose neutron irradiation can further accelerate the degradation of ferrite in a duplex stainless steel at the LWR relevant condition.
"Microstructural evolution of NF709 austenitic stainless steel under in-situ ion irradiations at room temperature, 300, 400, 500 and 600 °C" Chi Xu, Wei-Ying Chen, Yiren Chen, Yong Yang, Journal of Nuclear Materials Vol. 509 2018 644-653 Link
"Crack growth rate and fracture toughness of CF3 cast stainless stee at ~3 dpa" Yiren Chen, 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors August 13-17, (2017)