Effect of Elemental Synergism on the Mechanical Behavior of CoCrCuFeMnNi High-Entropy Alloy System

Co x CrCuFeMnNi (x = 0, 0.5, 1.0, 1.5, and 2.0 mol named as Co 0 , Co 0.5 , Co 1.0 , Co 1.5 , and Co 2.0 , respectively) and CoCr y CuFeMnNi (y = 0, 0.5, 1.0, 1.5, and 2.0 mol named as Cr 0 , Cr 0.5 , Cr 1.0 , Cr 1.5 , and Cr 2.0 , respectively) high-entropy alloys were prepared using vacuum hot pressing sintering technology. The effects of Co and Cr elements and elemental synergism on the alloys’ mechanical properties were studied. Results indicated that microhardness decreased with the increase in Co content but increased with the increase in Cr content. Compressive yield strength decreased with the increase in Co content, but plasticity increased considerably. As the Cr content increased, the yield strength of the alloys gradually increased, but their plasticity deteriorated. The strengthening mechanisms of the Co 0 alloys without Co and Cr 1.5 and the Cr 2.0 alloys with a high Cr content were mainly phase precipitation strengthening and FCC1 phase solid solution strengthening, respectively. The strengthening mechanism of the other alloys was mainly solid solution strengthening. The analysis of elemental synergism showed that Co equivalent (Co equiv ) had a remarkable impact on the mechanical properties of the high-entropy alloys, whereas Cr equivalent (Cr equiv ) had a small impact because the increase in Co equiv resulted in a much greater decrease in the strengthening phase (FCC1 + ρphase) than the increase in Cr equiv . Therefore, one of the effective ways to improve the mechanical properties of alloys is to comprehensively regulate the ratio of FCC- and BCC-forming elements by reducing Co equiv while rapidly increasing Cr equiv . Graphical Abstract