Effect of Ti content on microstructure and mechanical properties of TaMoNbCrTix refractory high-entropy alloy

Abstract

Refractory high entropy alloys (RHEAs) hold great promise for applications requiring high-temperature resistance. In this study, TaMoNbCrTix (x = 0, 0.25. 0.5, 0.75, 1) RHEAs were fabricated through mechanical alloying (MA) and spark plasma sintering (SPS). The effect of Ti content on the microstructure and mechanical properties of TaMoNbCrTix RHEAs was investigated. The results revealed that the alloys consisted of a body-centred cubic (BCC) matrix and Laves phase, with the addition of Ti promoting the formation of the Ti(O, N) phase. By employing severe deformation of the ball-milled powder, short sintering time, and the inhibition of precipitated phases on grain growth, the resulting RHEAs exhibited ultrafine grains measuring less than 1 μm. As the Ti content increased, the volume fraction of the Laves phase decreased, transitioning from a reticulated to a dispersed distribution. This shift had a positive influence on the ductility of the alloys. Among the studied compositions, TaMoNbCrTi0.75 displayed desirable comprehensive mechanical properties with yield strength, compressive strength, and fracture strain of 2696 MPa, 3098 MPa, and 16.8%, respectively. Notably, the ductility exhibited by TaMoNbCrTi0.75 at room temperature surpassed that of most Cr-containing RHEAs.