The structural relaxation and glass transition of LaAlNi and ZrAlCu amorphous alloys with a significant supercooled liquid region

Abstract

An amorphous phase with a wide supercooled liquid region, > 50 K, was found to form over wide composition ranges in the LaAlNi and ZrAlCu systems. The largest values for the temperature span between the crystallization temperature, T x, and the glass transition temperature, T g, ΔT x(- T x− T g), are 69 K for La 55 Al 25Ni 20 and 88 K for Zr 65Al 7.5Cu 27.5. The structural relaxation behavior on annealing was examined for the two amorphous alloys with the largest ΔT x values. The magnitude of the structural relaxation increases gradually with increasing annealing temperature, T a, and then rapidly in the T a range slightly below T g and decreases significantly on annealing T g. The rapid increase in the magnitude of the structural relaxation on annealing near T g is due to the glass transition. The single-stage structural relaxation indicates that there is no distinct difference in relaxation times (atomic bonding forces) between the constituent atoms in the two metal-metal-type amorphous alloys. The existence of an optimum bonding state is thought to cause the wide supercooled liquid region for the two amorphous alloys.