Effect of TiN on the microstructure and mechanical property of As-cast TiZrNbVAl lightweight high entropy alloy

The grain size of as-cast light weight high entropy alloy (LHEA) is required to be refined and its mechanical property should be improved further to satisfy its engineering application. In this paper, we investigated the effect of TiN on the microstructure and mechanical property of as-cast TiZrVNbAl LHEA with body-centered cubic (BCC) structure. TiN can serve as the potent nucleating agent, and reduce the grain size of as-cast ingot from 275 μm to 97 μm with 5 wt% addition. Part of TiN would dissolve during melting and reprecipitate again in the plate-like shape (∼0.3 μm thickness) at the grain interiors and grain boundaries during solidification, which could increase the strength but decrease the ductility. 3 wt% TiN addition can increase the yield strength of TiZrVNbAl LHEA near two times, from 804 MPa to 1603 MPa and maintain ∼25 % compression ductility. The significant strength improvement is ascribed to the synergy strengthening effect of TiN, interstitial N atom and refined grains. Our work is a valuable reference for the improvement of mechanical properties of as-cast BCC LHEAs.