Evolution of Substructure of a Non-equiatomic FeMnCrCo High Entropy Alloy Deformed at Ambient Temperature

The present investigation aims at discerning the evolution of microstructure of a Fe40Mn40Cr10Co10 high entropy alloy, under uni-axial loading at room temperature. At the time of quasi-static uni-axial loading, the alloy exhibited an ultimate tensile strength of similar to 514 MPa with fracture strain of similar to 47 pct. Multiple stages of work hardening were observed during the deformation. The initial work hardening of the alloy, for the true strain of epsilon similar to 0.05 to 0.1, was facilitated by the rigorous planar slip of dislocations. Extensive cell formation in the mid-strain levels, i.e., for epsilon similar to 0.1 to 0.29, resulted in overall softening. The onset of microband formation was also observed during the mid-strain level, which further got populated in large numbers during the final stage of deformation. Simultaneous occurrence of twins as well as deformation induced FCC -> HCP phase transformation was observed in the grains oriented along TD//< 111 > in the fractured specimen. Highly dense dislocation walls were also found at strain epsilon >= 0.29. The alloy showed an overall increase in work hardening before fracture, which was ascribed to the occurrence of twins, FCC -> HCP phase transformation, microbands, and highly dense dislocation walls. (C) The Minerals, Metals & Materials Society and ASM International 2019