Precipitation behavior and mechanical properties of a hot-worked TiNbTa0.5ZrAl0.5 refractory high entropy alloy

Abstract

A TiNbTa0.5ZrAl0.5 refractory high entropy alloy was prepared by powder metallurgy and subsequently subjected to hot forging. The precipitation behavior and its effects on compression properties were studied. Results show that the as-sintered TiNbTa0.5ZrAl0.5 alloy has a single BCC phase. The primary BCC phase is thermodynamically instable, and decomposes into BCC (Ti, Nb, Ta)-rich matrix and HCP (Zr, Al)-rich precipitates after hot forging. The precipitates are much harder than the matrix, and have significant strengthening effect. The hot-worked TiNbTa0.5ZrAl0.5 alloy has a high compressive yield strength of 1740 MPa with a considerable compressive ductility of 12% at room temperature. The precipitation strengthening contributes about 51% while the grain-boundary strengthening contributes 35% to the increment of the yield strength.