Displacement cascade under high-energy irradiation and tensile property in Fe-Cr-Al alloys: A molecular dynamics simulation

Abstract

Fe-Cr-Al alloy is considered as one of the most prospective accident-tolerant fuel cladding materials due to its excellently comprehensive properties. Irradiation performance evaluation of Fe-Cr-Al alloy is the key for successful development of fuel-clad system with enhanced accident tolerance. However, the microstructural response is largely dependent on irradiated conditions. In the present work, molecular dynamic method is employed to simulate the cascade collision processes under high-energy irradiation and tensile deformation behaviors of Fe-Cr-Al alloys. The threshold displacement energies (TDEs) in Fe-Cr-Al alloys are calculated at different temperatures and along various directions, and the TDEs along different directions exhibit significant anisotropy. The effect of alloy compositions on the displacement cascade of Fe-Cr-Al alloys is systematically studied, as well as the direction of the primary knock-on atom (PKA), temperature, and PKA energy. At 300 K and 700 K, no significant dependence between the number of surviving Frenkel pairs and PKA energies is observed in Fe-Cr-Al alloys under high-energy irradiation. High temperature and high-energy PKA could potentially lead to form large-sized interstitial clusters and a few small-sized vacancy clusters in Fe-Cr-Al alloys. Dislocations or dislocation loops can easily form at high temperatures and in high-energy irradiation. The effect of alloy compositions, temperatures and PKA energies on the tensile properties of Fe-Cr-Al alloys before and after irradiation, is systematically evaluated. By analyzing the corresponding yield strength, ultimate tensile strength and elastic modulus, Fe-Cr-Al alloys exhibit the characteristic of irradiation-induced hardening and embrittlement with the increase of PKA energy. As the temperature increases, the rigidity of alloys decreases while the irradiation embrittlement significantly increases.