Microstructure and mechanical properties of W-WC/Fe composite fiber-reinforced Fe matrix composite prepared by combination of infiltration and in-situ solid phase diffusion

To overcome the strength-toughness inversion relationship in steel/Fe matrix composites, a novel W-WC/Fe composite fiber-reinforced Fe matrix composite ((W-WC/Fe)f-IMC) with exceptional strength and toughness was fabricated by an in-situ fabrication method combining infiltration and in-situ solid-phase diffusion. The (W-WC/Fe)f-IMC consists of aligned W-WC/Fe composite fibers embedded in an Fe matrix. The W-WC/Fe composite fiber exhibits a characteristic core-shell structure on its cross section, with a resilient metal W fiber serving as the core and a robust annular WC-Fe layer acting as the shell. Due to the inward-outward growth and the gradient microstructure of the WC-Fe layer, the interface bonding strength between the W fiber/WC-Fe layer and the WC-Fe layer/matrix remains excellent. As a result, the (W-WC/Fe)f-IMC achieves an exceptional fracture strain of 35.5 ± 1.3 %, while maintaining high yield strength of 701 ± 16 MPa and ultimate compression strength of 1100 ± 18 MPa, surpassing those of cast Fe, which had values of 26.9 ± 1.1 %, 365 ± 20 MPa, and 834 ± 15 MPa, respectively. The simultaneous enhancement of the strength and toughness in (W-WC/Fe)f-IMC can be primarily attributed to the synergistic coupling effect between the high strength W-WC/Fe composite fibers and the tough matrix. The strategy proposed in this study holds promise as a method to alleviate the trade-off between strength and ductility in steel/Fe matrix composites.