The in-situ β phase reinforced Ti/Zr-based bulk metallic glass matrix composite by selective laser melting

In this study, in-situ β phase reinforced Ti/Zr-based BMGCs without toxic element Be, (Ti_0.65Zr_0.35-yNb_y)_100-xCu_x (x = 5, 10, y = 0.05, 0.1, at. %), were prepared via selective laser melting (SLM). The effect of Cu and Nb contents on phase formation, microstructure, and compressive mechanical properties were studied, and the microcrack formation mechanism in the deposits with lower Cu content (5 at. %) was also investigated. With the increase of Cu content from 5 to 10 at. %, the volume fraction of β phase decreased, while the volume fraction of amorphous phase and (Ti, Zr)₂Cu phase increased. Meanwhile, the amorphous phase presented a more continuous network-shaped morphology. Compared with the content of Cu element, the variation of Nb content had a minor effect on the phase precipitation and microstructure evolution. With the increase of Nb content, β phase became more stable, which may cause the increase of compression fracture strain. In addition, the microstructure with a good connectivity of β phase in the center zone of the molten pool had a higher deformation capacity than that in the edge zone of molten pool, where β phase was isolated by the amorphous phase network. There are some solidification microcracks existing in Cu5Nb4.75 and Cu5Nb9.5 deposits. Because of a higher |dT/d(f_S^1/2)| near f_S^1/2 = 1, the liquid phase cannot feed the liquid channel between β phases in time, liquid film is ruptured, and solidification crack forms.