An investigation on the microstructure and mechanical properties of Al0.3CoCrFeNi high entropy alloy with a heterogeneous microstructure

Abstract

In this study, the Al0.3CoCrFeNi high entropy alloy (HEA) with various heterogeneous microstructures was designed and fabricated through different process histories, such as severely cold-rolled plus annealing at low temperature for a long time (S1), cryo-rolled plus annealing at intermediate temperature (S2), cold-rolled plus annealing at intermediate temperature (S3). The microstructures were analyzed by SEM, EBSD, and TEM. The results showed that the heterogeneous grain structure of S1 alloy was composed of stretched original grains and fine recrystallized grains. Besides, the L12-(Ni, Co)3Al type phase was also observed within the face-centered cubic (FCC) matrix of the S1 alloy. However, the S2 and S3 alloys consisted of stretched original grains, survived original grains, fully recrystallized equiaxed grains, and B2 precipitates. Moreover, a mount of nano-deformation twins was also incorporated in the matrix of S2 alloy. Furthermore, the S2 alloy exhibited a superior balance of high ultimate tensile strength of ∼1019 MPa and high elongation of ∼28% as compared to S1 and S3 alloys due to its complex heterogeneous microstructure. This research would provide guidance for designing the heterogeneous structure in the FCC HEA and facilitate establishing the relationships between the heterogeneous structure and mechanical properties.