Enhanced thermal stability of Zr65Cu17.5Ni10Al7.5 metallic glass at temperature range near glass transition by oxygen impurity

The 'panoramic effects' of oxygen impurity on the thermal stability of Zr65Cu17.5Ni10Al7.5 metallic glass have been investigated by constructing time-temperature-transformation diagram and analyzing the precipitation kinetics of primary phase. It is found that oxygen has contrary effects on the alloy's thermal stability exhibiting in high- and low-temperature ranges because of primary phase selection. The primary phase for Zr65Cu17.5Ni10Al7.5 glassy alloy depends on its oxygen content as well as the temperature range in which crystallization takes place. For the alloy containing higher oxygen and crystallized at higher temperature, oxygen-induced metastable f.c.c.-Zr2Ni precipitates as primary phase. However, for the alloy with lower oxygen content, or with higher oxygen content but crystallized at lower temperature, stable b.c.t.-Zr2Cu forms as initial precipitation phase. Oxygen retards the precipitation of b.c.t.-Zr2Cu phase and stabilizes glassy matrix, enhanced thermal stability in the temperature range near glass transition is possessed by the alloy with higher oxygen. (c) 2007 Elsevier B.V. All rights reserved.