Ti (Zr)-Cu-Ni Bulk Metallic Glasses with Optimal Glass-Forming Ability and Their Compressive Properties

The formation of bulk metallic glasses (BMGs) was systematically investigated in the ternary Ti-Cu-Ni and quaternary Ti-Zr-Cu-Ni systems. Over a relatively wide composition range (50 to 57 at. pct Ti, 34 to 44 at. pct Cu, and 6 to 10 at. pct Ni) in the ternary Ti-Cu-Ni system, new Ti-based BMGs with a critical diameter of 1 mm have been discovered in the triangular region enclosed by the three intermetallic compounds TiNi, TiCu, and Ti2Cu. Partial substitution of Zr for Ti improved the glass-forming ability (GFA), and the BMGs of 3 mm in diameter were obtained in the composition range of 51 to 53 at. pct (Ti + Zr), 38 to 41 at. pct Cu, and 8 to 10 at. pct Ni. The enhanced GFA compared with the ternary Ti-Ni-Cu system was attributed to the effects of Zr on stabilizing the undercooled liquid. These Ti-based BMGs had compressive fracture strength higher than 2 GPa. Among them, the Ti50Cu43Ni7 glass exhibited a reproducible plastic strain larger than 5 pct.