Achieving balanced strength and ductility in a Fe64(CoCrNi)36 ferrous medium-entropy alloy via W addition

Abstract

The relatively low strength of ferrous medium-entropy alloys (Fe-MEAs) at room temperature has limited their widespread structural applications. In this study, a balanced strength and ductility were achieved in non-equiatomic [Fe₆₄(CoCrNi)₃₆]_100−xW_x (x = 0, 1, 2.5, and 4, at.%) Fe-MEAs via refractory tungsten (W) alloying and a single-step hot-rolling process. Increasing W content reduces the fraction of the body-centered cubic phase while promoting the formation of W-rich μ and minor Laves phases. The 4W alloy exhibits a yield strength of 810 MPa, an ultimate tensile strength of 891 MPa, and an elongation-to-failure of 26.3%. The improved yield strength is attributed to the combined effects of solid solution strengthening, grain boundary strengthening, dislocation strengthening, and precipitation strengthening. Detailed analysis revealed that the ductile face-centered cubic matrix effectively suppresses the propagation of microcracks originating from the hard and brittle precipitates. Furthermore, dislocation-precipitate/grain boundary interactions, nanoscale deformation twins, and deformation-induced martensitic transformation collectively improve the work-hardening capacity. These findings offer valuable insights into the design and development of cost-effective, high-performance Fe-MEAs for advanced structural applications.