On the microstructure, mechanical properties and wear resistance of an additively manufactured Ti64/metallic glass composite

Selective laser melting (SLM) provides flexibility in creating novel metal-matrix composites (MMCs) with unique microstructures and enhanced mechanical properties over conventionally manufactured MMGs. In this study, a Zr-based metallic glass (MG) decorated Ti6Al4V (Ti64) composite with a unique hybrid nanostructure and enhanced mechanical properties and wear resistance was fabricated using SLM. The results revealed that a near-full dense and crack-free Ti-based composite was produced, with its reinforcements consisting of ultrafine beta dendrites set with partially crystallized MG nanobands uniformly distributed along the boundaries of the melt pool. The addition of MG significantly affected the solidification behavior of the Ti-liquid because of its higher dynamic viscosity and density as well as compositional effect on the phase stability. With such a unique nanostructured reinforcement, the Ti64/MG composite exhibited an enhanced yield strength (> 1 GPa) with reasonable ductility and fracture toughness. On the basis of the result of a theoretical analysis, we attributed the main strengthening mechanism to Orowan strengthening. The wear resistance was also much improved in the Ti64/MG composite, arising from the higher hardness of the nanostructured reinforcement and the formation of a more protective tribo-oxide layer during sliding. The confinement of the 3D distributed reinforcement phase played a crucial role in preventing the delamination of the tribo-layer on the matrix. This work opens a pathway to the design of novel additively manufactured MMCs with outstanding mechanical properties.