FeCo-based multiphase composites with high strength and large plastic deformation

A family of FeCo-based multiphase composites with a microstructure consisting of nano-lamellar phase strengthened α-(Fe,Co) dendritic cores surrounded by a network of reinforcement phases of ultrafine eutectics was produced by copper mold casting. The hypoeutectic composites exhibit a high yield stress, which is up to 7 times higher than the equiatomic FeCo alloy, and plastic deformation up to 18% during compressive test. Multiscale o-(Fe,Co)3(B,C) reinforcement phases are responsible for the remarkable improvement of strength, and α-(Fe,Co) dendrites play a key role to inhibit the propagation of microcracks sourced from the eutectics. Furthermore, a fracture model for explaining the relationship between fracture strain and morphologic characteristics of the composites is presented.