Effect of carbon on microstructure and mechanical properties of Co-free medium-entropy alloys

Effect of carbon content on the microstructure and mechanical properties of a Co-free C x (CrFeNi) 100− x ( x = 0, 0.5, 1, 1.5, 3, 4.5, and 6 at.-%) medium-entropy alloys were systematically investigated. The increase of carbon content promoted the phase structure of alloys changing from a single FCC phase to an FCC + M 23 C 6 carbides dual-phase structure, accompanied by an apparent increase in yield strength and an uneven decrease in plasticity. The improvement of yield strength was attributed to the interstitial solid solution strengthening of carbon element and the precipitation strengthening of carbides. The decrease of plasticity was related to the formation of coarse carbides. The C 1.5 (CrFeNi) 98.5 alloy exhibited an enhanced yielding strength of 265 MPa while maintained a considerable elongation of 38%.