Study of the plastic deformation mechanism of TRIP-TWIP high entropy alloys at the atomic level

摘要

In this study, the deformation mechanism of Al-x (x = 0.5, 1.5)CrCoFeCuNi high entropy alloys (HEAs) during uniaxial tension at various strain rates and temperatures at the atomic scale was investigated. For this purpose, an atomic model of AlxCrCoFeCuNi HEA was built for melting and quick quenching and their mechanical behaviors were investigated. Based on polyhedral template matching (PTM) analysis, it was determined that for both the Al0.5CrCoFeCuNi and Al1.5CrCoFeCuNi, body cantered cubic (BCC) atomic structures were formed after solidification. The obtained stress-strain curves were discussed based on phase transformation from BCC to face-centered cubic (FCC) structure and vice versa (transformation-induced plasticity, TRIP), dislocation structure evolution, stacking fault (both intrinsic and extrinsic types, ISF/ESF) formation, and twinning/detwinning occurrence. It should be noted that SFs were detected based on HCP structure inside the FCC phase. The results were compared with experimental findings by a focus on nanotwins (NTs) and stacking faults (SFs) interaction with dislocations, and the effect of phase transformation on the promotion of twining boundaries. Finally, two plastic deformation mechanisms of TRIP-induced TWIP and TWIP-induced TRIP during stress fluctuation are shown and discussed.