Composition optimization of the Al–Co–Zr bulk metallic glasses

Abstract

Composition optimization for locating the composition with the largest glass forming ability in the Al–Co–Zr system is attempted in this investigation. The criteria that we have developed are respectively related to a specific conduction electron concentration, termed the e/ a-constant criterion, and to a specific cluster structure, termed the e/ a-variant criterion. For this system, the two criteria are incarnated into the composition line with constant e/ a=1.5 and the Co 4Zr 9–Al composition line. Bulk metallic glasses are obtained by suction casting for compositions with e/ a=1.3–1.5, with their thermal stabilities and glass forming abilities being increased with increasing e/ a ratios. The crossing point of the e/ a=1.5 line and the Co 4Zr 9–Al line gives the composition Al 23.5Co 23.5Zr 53 with the largest GFA (e.g. T g/ T m=0.637), superior to the reported Al 20Co 25Zr 55 alloy with T g/ T m=0.621.