Role of multi-variant deformation-induced HCP plates in cryogenic mechanical properties of an FCC high entropy alloy

We investigated the temperature-dependent mechanical properties and deformation mechanisms of the Fe49.5Mn30Co10Cr10C0.2Ti0.1V0.1Mo0.1 alloy from room temperature to cryogenic temperatures. As the deformation temperature decreased, both the strength and strain-hardening rate increased, while ductility tended to decrease. The higher strength of the material deformed at 123K, compared to that deformed at 223K, can be attributed to the larger number of multivariant HCP plates and higher hetero deformation induced (HDI) strengthening strengthening in the former. Multivariant deformation-induced HCP plates were the primary deformation mechanisms at all deformation temperatures, and cryogenic deformation activated intersecting shear, defined as the primary HCP plate being sheared by the secondary HCP plate. This mechanism contributed to stress relaxation and enhanced deformation accommodation. The reduced ductility observed in the material deformed at 123K may be attributed to coarse edge and grain boundary cracks, which were more pronounced when the TRIP effect was enhanced.