Best metallic glass former Al2Ni4Zr9 optimized by cluster-plus-glue-atom model

Cluster-plus-glue atom model and cluster-line criterion were employed to optimize the compositions of Zr-based Al–Ni–Zr alloys with superior glass-forming abilities (GFAs). Alloy series along the four composition lines, namely Ni3Zr7–Alx, Ni3Zr8–Alx, Ni3Zr9–Alx and Ni4Zr9–Alx (x = 1, 1.5, 2, 3) were designed and their GFA and thermal stabilities were investigated systematically in this work. It was revealed that the best glass former was Al2Ni4Zr9 (i.e., Al13.3Ni26.7Zr60 in atomic percent) alloy, where almost fully amorphous rod with a diameter of 10 mm could be obtained by copper mold suction casting. The GFA indicators, Tg/Tl (0.579) and γm (0.689), of the Al2Ni4Zr9 bulk metallic glass are all larger than those of the reported optimum Al15Ni25Zr60 glass former. Two cluster formulas [Ni–Ni2Zr9](Al2Ni1) or [Ni–Al2Zr9]Ni3 were tentatively proposed to explain the present optimal glass-forming composition Al2Ni4Zr9, where clusters Ni3Zr9 and Al3Zr9 (the central Al being replaced with Ni in the proposed formula) are derived from the Al2NiZr6 crystalline phase.