Effects of Annealing on Hardness, Yield Strength and Dislocation Structure in Single Crystals of the Equiatomic Cr-Mn-Fe-Co-Ni High Entropy Alloy

Abstract We report that in contrast to the anticipation, the macroscopic mechanical strength of single crystals of the face-centered-cubic single-phase equiatomic Cr-Mn-Fe-Co-Ni high entropy alloy is not influenced by thermal annealing during which short-range ordering is expected to develop. Experimental evidence shows that hardness at room temperature, critical resolved shear stress at room temperature and at 77 K and activation volume values of the alloys do not significantly vary with the annealing temperature in the range from 900 to 1200°C. The stacking fault energies in the specimens deformed at 77 K following annealing at 1000 and 1200°C respectively are essentially identical to each other. These results clearly indicate that the impact of the formation of chemical short-range order on the macroscopic yield strength of the equiatomic Cr-Mn-Fe-Co-Ni high entropy alloy is insignificant, even if it exists.