Design of a low density refractory high entropy alloy in non-equiatomic W-Mo-Cr-Ti-Al system

A new refractory high entropy alloy (RHEA) with non-equiatomic composition of W10Mo27Cr21Ti22Al20 was designed based on empirical rules and CALPHAD approach. Calculated results showed that W10Mo27Cr21Ti22Al20 RHEA had lower density and higher melting temperature than that of equiatomic alloy. The designed alloy was prepared by vacuum arc melting then the crystal structure, microstructure, chemical composition, density, hardness and compressive strength had been evaluated. The alloy exhibited a BCC solid solution as major phase with typical dendritic microstructures. The experimental results confirmed calculated results, suggesting a BCC solid solution phase. The density of the alloy was 7.48 g/cm(3), which was approximately close to the calculated value, 7.61 g/cm(3). However, the measured hardness value (511 kg/mm(2)) was significantly higher than the calculated value (125 kg/mm(2)), indicating the effect of solid solution strengthening. This alloy had compressive yield strengths of 1245 MPa at room temperature, 510 MPa at 600 degrees C, 201 MPa at 1000 degrees C and 105 MPa at 1200 degrees C. Compressive strain of the alloy was limited at room temperature, but it increased significantly to above 60% at 1000 degrees C and 1200 degrees C. Comparing with four conventional superalloys Inconel 718, Waspaloy, Hastaloy X and Haynes 230, the studied RHEA shows lower density and superior high-temperature yield strength.