Enhanced strength-ductility synergy in a Cu-based high entropy alloy via severe cold-deformed and annealing treatment

The distinctive microstructural properties of high-entropy alloys provide an opportunity to develop alloys with exceptional strength and ductility. As a typical Cu-based high-entropy alloy, the equiatomic CoCrFeNiCu alloy is desirable for aerospace and nuclear applications due to its excellent high-temperature wear resistance and radiation resistance. This study successfully achieved an excellent balance of strength and ductility in the CoCrFeNiCu alloy through severe cold-deformed and subsequent annealing treatment. Mechanical properties were evaluated using tensile testing, while microstructural evolution was systematically characterized via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). After severe cold deformation, the yield strength and ultimate tensile strength reached 873 MPa and 931 MPa, respectively, representing increases of 3.2 and 2.2 times increase compared to the as-cast alloy. However, the elongation decreased significantly from 35.27 % to 2.12 %. Following annealing treatment at 1110 °C for 120 min, elongation increased to 35.98 %. The results showed that the yield strength and ultimate tensile strength were 1.4 and 1.6 times greater than those of the as-cast alloy, accompanied by a slight increase in elongation. The CH-1100 sample exhibited fine equiaxed grains with an average size of approximately 7.3 μm, and numerous rod-like nano-sized Cu precipitates measuring about 20 nm were observed. The synergistic effects of grain refinement, dislocation strengthening, and precipitation hardening contributed to the simultaneous enhancement of both strength and ductility in the CoCrFeNiCu alloy.