The Precipitation Behavior in Al0.3CoCrFeNi High-Entropy Alloy Affected by Deformation and Annealing

The effects of deformation and annealing on the precipitation behaviors, including the structure and chemical composition of the L1(2), B2, BCC and sigma phases, in Al0.3CoCrFeNi high entropy alloy were analyzed. Firstly, the thermodynamic factors controlled the precipitation pathway in as-cast alloys, which led to the L1(2) precipitating homogeneously in the FCC matrix under a low annealing temperature, while the B2 precipitated under a high annealing temperature. In contrast, if the deformation was introduced before annealing, the precipitation pathway of the second phase was completely changed to the B2, BCC and sigma phases because of the combination of thermodynamic and kinetic conditions. In particular, the B2 and sigma phases promoted the precipitation behavior reciprocally due to the complementary chemical compositions. The elaborate precipitation behaviors of the L1(2), B2, BCC and sigma phases were analyzed to identify the phase transformation in the Al0.3CoCrFeNi HEA. These transformation pathways and elaborate structural features of the L1(2), B2, BCC and sigma phases provide various design possibilities for the microstructures and properties of single FCC HEAs.