Effect of Al Contents on Microstructure and Mechanical Properties of Alxcocrfenimo0.3 High-Entropy Alloys

Abstract

In this work, AlxCoCrFeNiMo0.3 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) high-entropy alloys were prepared with high-vacuum arc melting method, and the effect of Al contents on the microstructure and mechanical properties of the alloys was investigated. The experimental results exhibit that the phase structures of alloys evolved from FCC + σ to FCC+ σ +B2 with the increase of Al content. And the dendritic structure of alloys experiences a refinement process, during which the most significant refinement is observed at x=0.2. At x=0.5, the dendritic structure disappeared entirely, resulting in a microstructure that resembles the Widmanstätten structure morphology. The mechanical test results show that the indexes of microhardness, tensile strength Rm, yield strength Rp0.2, and elongation A of the alloys all improved with the increase of Al content. Among them, the Rm and A of Al0.2CoCrFeNiMo0.3 alloy are 656.81 MPa and 14.56%, respectively, exibiting the better match in terms of both properties. Meanwhile, the addition of Al element could promote the formation of sub-grain boundaries in the σ phase grains of the alloy, which is beneficial to the design of a uniformly dispersed σ phase. The above results also can provide a theoretical basis for the further engineering application of high-entropy alloys.

Keywords: High-entropy alloys (HEAs), microstructure, mechanical properties, second phase, grain refinement