Effect of V Content on Phase Formation and Mechanical Properties of the CoFeNiMnVx High-Entropy Alloys

The sigma phase (sigma phase) helps to enhance the mechanical properties of high-entropy alloys (HEAs). In this study, several CoFeNiMnVx (x = 0.25, 0.50, 0.75, 1.00, 1.25, and 1.50) HEAs were synthesized using vacuum arc melting to improve the strength of face-centered cubic (FCC)-type CoFeNiMn HEAs. Vanadium (V)'s influence on the microstructure evolution and compressive properties is investigated. Further, only a single-phase FCC solid solution is observed for alloys with x <= 1.00. In contrast, a mixture of FCC solid solution and intermetallic sigma phase is observed for alloys with x > 1.00. The FCC phase lattice constant first increases and then decreases slightly with an increase in V content. Adding V improves the strength and microhardness of FCC-type CoFeNiMn HEAs but decreases their ductility. As V content increases, the yield strength significantly increases from 223 to 1545 MPa, whereas the fracture strain decreases from >55% (no fracture) to about 9.5%. Increasing V content also results in an increase in microhardness from 213 to 716 HV.

Automated summary

Vanadium (V) significantly affects the mechanical properties of high-entropy alloys, increasing V content can significantly improve the yield strength and microhardness of the alloys but decreases their ductility. When V content is greater than 1.00, a mixture of FCC solid solution and intermetallic sigma phase is observed in the alloys.