Dynamic mechanical responses of the Al0·1CoCrFeNi high entropy alloy at cryogenic temperature

Abstract

In this work, dynamic compression experiments are carried-out at both room temperature (RT = 298 K) and liquid nitrogen temperature (LNT = 77 K) to systematically investigate the dynamic mechanical responses of the Al0·1CoCrFeNi high entropy alloy (HEA). The yield strength significantly increases with the increasing strain rate. Even higher yield strengths are revealed when the temperature decreases from 298 K to 77 K. At cryogenic temperature, abundant nanoscale deformation twins are observed due to lower stacking fault energy (SFE). By introducing new interfaces in the grains and decreasing the mean free path of dislocations during deformation, the high density deformation twins that formed during dynamic deformation at 77 K lead to a higher degree of strain hardening rate. In addition, the low SFE results in widely dissociations and reactions of dislocations, which lead to the formation of Lomer-Cottrell (L-C) and Lomer dislocation locks. These immobile dislocation locks can act as both dislocation sources and barriers, which can also contribute to the outstanding strain hardening capability of the Al0·1CoCrFeNi HEA upon dynamic deformation at 77 K.