Effects of C and Mo on microstructures and mechanical properties of dual-phase high entropy alloys

Abstract

A systematic study of the effects of interstitial element C and high melting point element Mo on the microstructural evolution and mechanical properties of dual-phase CoCrFeNiAl0.5 high entropy alloys (labeled as HEAs) is presented. In order to obtain a fine-grained microstructure, the HEAs were produced by powder metallurgy (P/M) method. Microstructures and mechanical properties were characterized using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), electron probe microanalysis (EPMA) and tensile tests. The results show that, with the addition of C and Mo, all the P/M HEAs exhibit a fine equiaxed microstructure. A small amount of carbides and σ phase are distributed evenly on the HEA matrix. The CoCrFeNiAl0.5 HEA containing 8 at. % of Mo and C shows combined high strength of 1280 MPa and reasonable ductility of 7.1%. The improvement of the tensile strength is caused by the solid solution strengthening, fine-grained strengthening and precipitation strengthening. The good ductility results from the fine-grained microstructure.