Effect of carbon on microstructure and mechanical properties of Fe36Mn36Ni9Cr9Al10 high-entropy alloys

The effect of C-alloying on phase constituent, microstructure and mechanical behaviour of a novel Co-free (Fe 36 Mn 36 Ni 9 Cr 9 Al 10 ) 100-x C x (x = 0, 1.5, 2.5, 3.5, 5, 6) low-cost high entropy alloy (HEA) system was investigated. Addition of carbon promoted the transformations of BCC and B2 phase in the original C-free HEA into FCC phase. At a carbon content of 2.5 at.-% and beyond, hardly BCC phase constituent can be obtained. Optimised mechanical properties with a yield strength of 387 MPa, tensile strength of 741 MPa along with excellent ductility of 57% were achieved at a carbon content of 2.5 at.-%. The improvement in mechanical properties of the (Fe 36 Mn 36 Ni 9 Cr 9 Al 10 ) 97.5 C 2.5 HEA can be ascribed to enhance the work hardening ability originated from microband-induced plasticity effect.