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

Composition optimization for locating the composition zone with the largest glass forming ability (GFA) in the Zr-Al-Co system is attempted. The criteria that we have developed are respectively related to the conduction electron concentration, termed the e/a-constant criterion, and to the special cluster structure, termed the e/a-variant criterion. For this system, the two criteria are incarnated into the e/a-constant line. with constant e/a=1.5 and the (Zr9Co4)-Al and (Zr(78.)5Co(21.5))- Al e/a-variant lines. Bulk metallic glasses (BMGs) are obtained by suction casting for alloys on the (Al50Co50)-Al e/a-constant line and (Zr9Co4)-Al e/a-variant line. On the (Zr9Co4)-Al e/a-variant line, the thermal stability and glass forming. ability of BMGs are increased with increasing e/a ratio. The Zr53Al23.5Co23.5 BMG with the largest thermal stability and GFA locates in the intersecting point of the two lines, its characteristic thermodynamic indices are T-g=783 K, T-x=849 K, T-g/T-m=0.637, T-g/T-l=0.590.