Effect of Microstructures and Mechanical Properties of Large Deformation High Entropy Alloy CoCrCuFeNi in Semi-solid Isothermal Heat Treatment

The semi-solid slurries of the CoCrCuFeNi high entropy alloy (HEA) were fabricated through the recrystallization and partial melting (RAP) process by cold-rolling and partial remelting. The temperature range of the semi-solid region and the relationship between the liquid fraction and the temperature were determined by the differential scanning calorimetry (DSC) curve. The effect of isothermal temperature and holding time on the evolution of the microstructure and mechanical properties of the rolled samples was analyzed. The results show that the microstructure was significantly deformed, and the tensile strength has been increased by 107% after 63% rolling deformation of the CoCrCuFeNi high entropy alloy (HEA). The high-entropy alloy after cold rolling was maintained at 1150 and 1300 ° C for 20, 30, 60, and 120 minutes respectively, the plasticity has been improved compared with the rolled high entropy alloy. The optimal plasticity was reached 13.7% and 7.9% at 1150 ℃ and 1300℃ for 30 minutes, respectively. After semi-solid isothermal heat treatment, the grain morphology changed from dendritic of as-cast or rolled to spherulite and the grain size increased significantly with time and the holding temperature increased.