Glass Formation in Ni-Zr-(Al) Alloy Systems

Abstract

Structural and thermal properties of binary Ni 100 - x Zr x ( 30 < x < 75 ) alloys obtained by melt spinning and copper mold casting methods were investigated. The fully amorphous samples in a bulk form cannot be obtained in the binary Ni-Zr alloys over a wide composition range, though they have T g / T l and γ values close to or even higher than those of the binary Cu-Zr bulk metallic glasses (BMGs). The low thermal stability of the supercooled liquid against crystallization and the formation of the equilibrium crystalline phases with a high growth rate are responsible for their low glass-forming abilities (GFAs). Relatively low thermal conductivities of Ni-based alloys are also considered to be another factor to limit their GFAs. The GFA of the binary Ni 65.5 Zr 34.5 alloy alloyed with 4% or 5% Al was enhanced, and a fully glassy rod with a diameter of 0.5 mm was formed.