Cu–Zr–Al (Ti) bulk metallic glasses: Cluster selection rules and glass formation

Abstract

The present paper investigates the bulk metallic glass formation in Cu–Zr–Al and Cu–Zr–Ti ternary systems by using the cluster line criterion. The binary basic clusters are first selected for constructing cluster lines. Three cluster selection rules are proposed: topologically dense packing, chemical short-range order and composition distance to deep eutectics. Three Cu–Zr clusters Cu 8Zr 5, Cu 6Zr 5 and Cu 5Zr 6 are selected according to the three rules. The bulk metallic glass-forming ranges in these two systems are determined. The thermal characteristic parameters of the Cu–Zr–Al BMGs on every composition line increase with increasing Al content and decrease with increasing Ti content in the Cu–Zr–Ti glass-forming range. The optimum bulk amorphous compositions in the Cu–Zr–Al system are Cu 58.1Zr 35.9Al 6 and Cu 39.7Zr 47.1Al 13.2, respectively, located in Cu 8Zr 5–Al and Cu 5Zr 6–Al cluster lines. In the Cu–Zr–Ti system, the Cu 64Zr 28.5Ti 7.5 composition with the largest T g/ T l is located in Cu 9Zr 4–Ti cluster line and the Cu 57.6Zr 32.4Ti 10 composition with the largest glass-forming ability is located in Cu 64Zr 36–Ti line.