Combined effect of silicon doping and thermal treatment on microstructures and mechanical properties of Ti50Nb20V20Al10 refractory high-entropy alloy

Abstract

This study investigates the effects of Si doping and thermal treatment on the microstructures and mechanical properties of Ti50Nb20V20Al10 refractory high-entropy alloy (RHEA) with a BCC/B2 dual-phase structure. The as-cast RHEAs exhibit typical dendrite and inter-dendrite structure. Upon Si doping, eutectic M5Si3 phase gradually precipitates along the grain boundaries (GBs), resulting in the increase of yield strength (YS) by over 200 MPa. After recrystallization, all the RHEAs exhibit fully recrystallized microstructures. The eutectic M5Si3 phase disappears while forming nanoscale M5Si3 phase distribute along GBs, thereby enhancing the mechanical properties of the RHEAs. Notably, the recrystallized RHEA with 1 at% Si exhibits favorable specific YS (SYS, 172.9 ± 2.9 MPa·cm3·g−1) and fracture elongation (22.8 ± 6.8 %), respectively. The hindrance effect of nanoscale M5Si3 phase on dislocations motion and the transition from planar slip to cross-slip significantly enhance strain hardening capability and plasticity of the RHEAs. Our research findings are of constructive significance to the study of lightweight energetic structural materials.