Effect of Cu content on microstructure and mechanical properties of in-situ β phases reinforced Ti/Zr-based bulk metallic glass matrix composite by selective laser melting (SLM)

In this study, non-toxic in-situ β phases of reinforced Ti/Zr-based bulk metallic glass matrix composites (BMGCs) of (Ti_0.65Zr_0.35)_100-xCu_x (x = 5, 10, 15 at.%) are fabricated via selective laser melting. The effect of Cu content on phase formation, microstructure, and mechanical properties is investigated. The average volume fraction and width of the β phase decreases with increasing Cu content, while a more amorphous phase and the (Ti, Zr)₂Cu phase forms. In the center zone of the molten pool, the β phase grows in the direction of the temperature gradient, and the amorphous phase distributes among the β phases. This occurs using: sphere morphology (for x = 5), a more continuous elongated sphere and network morphology (for x = 10), and network morphology (for x = 15), respectively. In the edge zone of the molten pool, due to the smaller cooling rate and the existence of a partially molten zone, the β phase becomes coarser, and an amorphous phase forms for more continuous networks. Furthermore, the hardness improves significantly with increasing Cu content. No crack is found for x = 5. Although the average volume fraction of the β phase for x = 5 is about 90 %, the compression yield strength is 1386 ± 64 MPa, reaching to an average level of conventionally fabricated counterparts, due to finer microstructure, and twinning and martensitic transformation of the β phase.