Improvement of mechanical properties of CoCrFeNiAl0.5 high-entropy alloys treated by double heat-treatment process

This study systematically investigates the influence of three heat-treatment processes including aging, annealing, and annealing + aging on the microstructure and mechanical properties of cold-rolled CoCrFeNiAl 0.5 high-entropy alloys. The experimental results indicate that the double heat-treatment process (1050 °C annealing + 650 °C aging) can effectively suppress intragranular segregation, increase the BCC/B2 phase content, and enhance the alloys hardness (∼ 349.9 HV). Meanwhile, the numerous coherent L1 2 phase precipitates in the annealing twinning and FCC matrix phases, resulting in ordered strengthening and coherent strain strengthening. The B2 phase precipitates at the BCC and FCC phase boundaries with different sizes, and dislocations move via bypass and shear mechanisms, respectively. These two factors significantly enhance the alloy’s strength and plasticity, with the yield strength R p0.2 , tensile strength R m , and elongation at fracture A reaches 859 ± 23.8 MPa, 1177 ± 33.9 MPa, and 26 ± 2.8%, respectively. In brief, compared with single aging or annealing treatment processes, the CoCrFeNiAl 0.5 high-entropy alloys treated by double heat-treatment process, due to their excellent strength-ductility matching, possess significantly potential applications in practical engineering fields such as special components for equipment, critical material devices, etc.