Effect of V content on the microstructure and mechanical properties of HPT nanostructured CoCrFeMnNiVx high entropy alloys

The article presents investigations of microstructure and low‐temperature mechanical properties of nanostructured alloys CoCrFeMnNiV x ( x = 0.15–0.75), processed by high‐pressure torsion (HPT) at temperatures of 300 and 77 K. While at x ≥ 0.5 the values of microhardness ( H v ) and compression yield stress ( σ 0.2 ) in samples after HPT at 77 K are larger than those in samples after HPT at 300 K, for x ≤ 0.2 surprisingly the opposite effect is observed. As in case of the undeformed CoCrFeMnNiV x alloys, the behavior for vanadium concentrations x ≥ 0.5 can be related to the formation of tetragonal σ‐phase in addition to face‐centered cubic matrix, while the anomalous behavior for x ≤ 0.2 arises from the formation of HPT‐induced hexagonal martensitic phase. In the low‐temperature ranges, i.e., 20–300 K in case of HPT nanostructured CoCrFeMnNiV 0.2 , and 150–300 K in case of HPT nanostructured CoCrFeMnNiV 0.5 , dependences of σ 0.2 ( T ) show characteristics of thermally activated dislocation movement. For the first time in high‐entropy alloys, anomalous dependences of σ 0.2 ( T ) at temperatures 4.2–20 K for CoCrFeMnNiV 0.2 , and at 80–150 K for CoCrFeMnNiV 0.5 are found, which indicate at the occurrence of nonthermal inertial dislocation movement.