Microstructure and Mechanical Properties Evolution of W@WC/Fe Core–Shell Bar‐Reinforced Iron Matrix Composites: Effect of In‐situ Solid Diffusion Time

To improve the strength and toughness of conventional particle‐reinforced iron matrix composites, W@WC/Fe core–shell bar‐reinforced iron matrix composites (CBIMCs) are synthesized by casting and in‐situ solid‐phase diffusion method. These composites, which have an architecture similar to concrete, consist of a core of residual W bar and a shell of gradient‐structured WC‐Fe layer. The effect of in‐situ solid diffusion time on the evolution of microstructure and mechanical properties of the composites is investigated. It is observed that for in‐situ solid diffusion times ranging from 3 to 24 h, the reinforcement in the composites remained as W@WC/Fe core–shell bars. As the solid diffusion time increased, the diameter of the W core gradually decreased, and the thickness of the WC‐Fe shell layer increased. At a solid diffusion time of 30 h, the reinforcement transitioned to the WC‐Fe composite bar. Additionally, with longer solid diffusion times, the WC particles transformed from a triangular prism shape to a truncated octahedron. The composite prepared at 18 h exhibits the highest ultimate compression strength and strain, reaching values of 1100 ± 18 MPa and 35.5 ± 1.3%, respectively. This excellent ultimate compression strength is mainly due to the WC particles, which enhanced load transfer strengthening and dislocation strengthening. Moreover, the metal W core and iron matrix effectively hinder microcrack propagation, thus contributing to the enhanced toughness of the composite.