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

TLDR

The supercooled liquid stability near stoichiometric Al₁La₂Ni₁, shown by a large ΔTₓ and high T_g/T_m, appears to arise from optimal bonding among the constituent atoms. Variations in crystallization temperature and hardness with composition are attributed to changes in atomic configurations involving La₃(Al,Ni), La(Al,Ni), and La(Al,Ni)₂ compounds. Amorphous Al–La–Ni alloys produced by melt spinning exhibit a wide supercooled liquid region (ΔTₓ up to 69 K) and high reduced glass transition temperature (up to 0.68) across a broad compositional range (3–83 at % La, 0–60 at % Ni), with higher Al and Ni contents increasing Tx, hardness, and tensile strength.

Abstract

Amorphous alloys exhibiting a wide supercooled liquid region and a high reduced glass transition temperature (Tg⁄Tm) 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 ΔTx(=Tx−Tg) between Tg and crystallization temperature (Tx) reaches as large as 69 K for Al25La55Ni20. The Tg⁄Tm 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 Tx and hardness (Hv) 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 Tx and Hv 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 ΔTx and high Tg⁄Tm, seems to result from an optimum bonding state of the constituent atoms for the stoichiometric alloy.