Zr–Al–Ni Amorphous Alloys with High Glass Transition Temperature and Significant Supercooled Liquid Region

Abstract

Amorphous Zr–Al–Ni alloys exhibiting a wide temperature region of supercooled liquid state and a high reduced glass transition temperature (T_g⁄T_m) were formed over a composition range from 0 to 37 at% Al and 3 to 67%Ni by melt spinning. The temperature span ΔT_x(=T_x−T_g) between T_g and crystallization temperature (T_x) reaches as large as 77 K for Zr₆₀Al₁₅Ni₂₅. The T_g⁄T_m is also as high as 0.64 in the vicinity of Zr₆₀Al₂₀Ni₂₀ and their Zr–Al–Ni alloys are concluded to have a large glass-forming capacity. The T_x and hardness (H_v) increase with increasing Al and Ni contents in the range from 660 to 860 K and 400 to 720, respectively, and the tensile strength also has a similar compositional dependence in the range of 1335 to 1720 MPa. The compositional effect on T_x and H_v was presumed to originate from the variation of the atomic configuration which reflects the equilibrium compounds, because of the similarity in the compositional dependence among T_x, H_v and the melting temperature of the compounds. The high thermal stability of the supercooled liquid in the vicinity of Zr₃Al₁Ni₁ seems to result from optimum bonding and packing states of the constituent atoms in the limited alloy.