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

Abstract

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 β 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.