Achieving balanced mechanical properties in additively manufactured maraging steel matrix composites through phase engineering

In this work, we demonstrate a phase engineering strategy, based on a composite design of monomorphic diamond (MD) reinforced FV520B maraging steel, for controlling matrix phase constituents with high strength and ductility. Benefiting from the enhanced grain growth rate induced by the MD addition, the solidification structure transition from planar to cellular and further to dendritic was achieved. The dissolved MD solute modifies the martensite-to-austenite transformation kinetics, promoting the stabilisation of a predominantly austenitic phase structure. Meanwhile, the elemental segregation around the cellular structure contributes to the massive formation of the M23C6 carbides. Consequently, the microstructural changes due to the MD particle addition result in an exceptional synergy of strength and ductility. This work provides a promising way to fabricate dispersion-strengthened maraging steels with high overall performance.