Deformation behavior and strengthening mechanisms of high-entropy alloys under high strain rate across wide temperature ranges

Abstract

This study systematically investigates the deformation mechanism and strengthening effects of the CoCrFeNiMn_0.75Cu_0.25 high-entropy alloy (HEA) under dynamic tensile loading across a wide temperature range (93 K to 1073 K). The HEA exhibits a ∼30% enhancement in strength and ductility at 93 K relative to its performance at 298 K. These superior properties result from the synergistic interactions among deformation bands, stacking faults (SFs), multiscale twinning, dislocations, and Lomer-Cottrell (L-C) locks, which enhance work hardening and delay fracture. At 873 K, dislocation slip becomes dominant, and dynamic recovery is activated, facilitating stress redistribution and more uniform macroscopic deformation. At 1073 K, discontinuous dynamic recrystallization (DDRX) occurs within deformation bands, producing refined grains that redistribute stress and maintain elongation above 60%, ensuring superior plasticity despite thermal softening. These findings indicate that temperature strongly influences microstructural evolution, with thermally activated dislocation motion, recovery, and recrystallization playing critical roles in determining the deformation response at high strain rates. This study provides new insights into the temperature-dependent strengthening mechanisms in HEAs, which have implications for the development of advanced materials for extreme environments.