Al–La–Ni Amorphous Alloys with a Wide Supercooled Liquid Region

Abstract

Amorphous alloys exhibiting a wide supercooled liquid region and a high reduced glass transition temperature (T_g⁄T_m) were found to be formed over a compositional range from 3 to 83 at% La and 0 to 60%Ni in Al–La–Ni system by melt spinning. The temperature span ΔT_x(=T_x−T_g) between T_g and crystallization temperature (T_x) reaches as large as 69 K for Al₂₅La₅₅Ni₂₀. The T_g⁄T_m is also as high as 0.68 for Al₂₅La₅₅Ni₂₀ and the Al–La–Ni alloys are concluded to have a high glass-forming ability. The T_x and hardness (H_v) increase with increasing Al and Ni contents in the range from 425 K to 750 K and 170 to 520 and the tensile strength also has a similar compositional dependence in the range of 515 to 795 MPa. The compositional effect on T_x and H_v was presumed to originate from the variation of the atomic configuration which reflects the compounds of La₃(Al, Ni), La(Al, Ni) and La(Al, Ni)₂. The high stability of the supercooled liquid in the vicinity of the stoichiometric composition Al₁La₂Ni₁ against the transformation of crystalline phases, i.e., large ΔT_x and high T_g⁄T_m, seems to result from an optimum bonding state of the constituent atoms for the stoichiometric alloy.