Microstructural Verification, Mechanical and Wear Analysis of MoTaNbV_xTi Refractory High-Entropy Alloys

MoTaNbV_xTi (x = 0.25, 0.50, and 0.75 at.%) refractory high-entropy alloys were synthesized via vacuum arc melting. The cross-sectional microstructural investigation revealed a Ti segregation tendency in the interdendritic area and a mostly homogeneous distribution of the rest elements in the dendritic parts. The calculated empirical models further verified the aforementioned microstructural evidence. Regarding the alloys’ mechanical investigation, both Vickers microhardness and Rockwell hardness estimations were escalated to values higher than those of the constituent elements, suggesting the operation of a solid solution strengthening mechanism. In terms of compression, the alteration of V content seemed to affect the alloys’ response, since the alloys with increased V content exhibited improved properties. The fracture surfaces presented cleavage/tearing characteristics, with the river-like patterns’ presence, defining their modes. In terms of their work-hardening rate, the alloys exhibited two regimes during the compression test due to possible changes in the deformation mechanisms. Finally, wear rate values verified that the harder the alloy (increased V content), the greater the wear resistance.