Strength–ductility synergy effects in titanium matrix composites reinforced with Fe₃O₄-coated graphene

Loss of toughness in titanium matrix composites (TMCs) is often inevitable, as strength enhancement typically comes at the expense of ductility, especially for brittle ceramic reinforcements induced by interfacial chemical reaction. To fully exploit the strengthening potential of nanocarbons in TMCs and maintain ductility, it is critical to mitigate the in-situ reactions between nanocarbons and titanium. This study proposes an inspired strategy by reinforcing Ti–6Al–4V (Ti64) matrix with graphene oxide (GO) decorated with Fe₃O₄ nanocrystals (Fe₃O₄@GO/Ti64). This design achieves 41.6% improvement in toughness, with simultaneously enhanced strength and elongation, compared to that of Ti64 alloy. Uniform Fe₃O₄ coatings (∼20 nm) were distributed on the GO surface and subsequently consumed during consolidation via reaction with the Ti matrix, thereby preserving GO. Microstructural analysis of plastic deformation revealed that elongation was primarily attributed to the dislocation slip bands, grain boundary sliding and twins, while the in-situ TiC inhibited slip-band motion. The estimated strengthening factors illustrated that solid-solution strengthening dominated the enhanced strength in all composites. Furthermore, the Fe₃O₄@GO/Ti64 composites exhibited significantly enhanced load transfer effects compared with GO/Ti64, due to the Fe₃O₄ modificative coatings. These findings underscore the crucial role of interfacial decoration and solid-solution mechanisms in improving the overall mechanical performance of the TMCs, while also highlighting their economic and environmental potential in lightweight metallic design.