Enhancement of Thermal Stability by Oxygen Impurity for Vitreloy 105 Metallic Glass

Abstract:

A ‘panoramic effect’ of oxygen impurity on the thermal stability and GFA of Vitreloy 105 metallic glass was investigated based on the construction of TTT diagram and the kinetics analysis of primary phase precipitation. It was found that the oxygen impurity has different influences on the alloy’s thermal stability and GFA in the content range of 0.015 %~0.045 % (mass) because the primary phase was changed. The oxygen decreases the alloy’s GFA during continuously cooling crystallization for the oxygen-induced f.c.c.-Zr2Ni precipitates as the primary phase. However, the oxygen retards the precipitation of b.c.t.-Zr2Ni phase and enhances the alloy’s thermal stability during the reheating recrystallization of glassy alloy for the b.c.t.-Zr2Ni as the initial precipitation phase. The crystal structure of primary phases depends on the conditions for oxygen diffusion during the crystallization above nose temperature, Tn, and the recrystallization below Tn

Key words:bulk metallic glasses; thermal stability; crystallization kinetics; primary phase; oxygen impurity