Temperature dependent deformation behavior and strengthening mechanisms in a low density refractory high entropy alloy Al10Nb15Ta5Ti30Zr40

Abstract

A low-density high entropy alloy Al10Nb15Ta5Ti30Zr40 has been developed which exhibits excellent compressive room temperature ductility, despite the presence of Al. Microstructure, room temperature and elevated temperature mechanical properties of this newly-designed alloy have been reported in as cast and heat-treated conditions. The homogenized and continuously cooled (water quenching or air cooling) conditions of this alloy consist of a nanoscale mixture of a disordered BCC and an ordered B2 phases, while subsequent low temperature annealing treatment leads to the formation of additional phases. In the homogenized condition, the yield stress of the alloy is 1050 MPa at 23 °C, 852 MPa at 400 °C and 1059 MPa at 600 °C. Above 600 °C, the yield stress decreases rapidly with increasing temperature becoming 250 MPa at 800 °C and less than 50 MPa at 1000 °C and 1200 °C. Correlations between the mechanical properties and microstructure, as well as temperature-dependent operating strengthening mechanisms, are also discussed in this paper.