Effects of annealing temperature and cooling medium on the microstructure and mechanical properties of a novel dual phase high entropy alloy

Effects of annealing temperature and cooling medium on the hexagonal close-packed (HCP) phase fraction and mechanical properties of a novel Co35Cr25Fe37.5Ni2.5 alloy are investigated. The uniformly initial grain size and different HCP phase fractions are obtained via the same annealing temperature and different cooling mediums. The HCP phase area fraction is doubled as the cooling medium of water is replaced by liquid nitrogen, and the main reason is the rapid increase of nucleation sites of liquid nitrogen cooling. HCP laminates with different orientations intersect within grains. The yield strength and ultimate tensile strength of Co35Cr25Fe37.5Ni2.5 alloys annealing at 900 °C with liquid nitrogen quenching are ~482 MPa and ~1079 MPa, respectively. Contributions of the FCC phase and HCP phase to yield strength are discussed. The results indicate the combination of annealing temperature and cooling medium is an efficient manipulation method to adjust the HCP phase fraction and mechanical properties of dual phase high entropy alloy.