Effect of Oxygen Impurity on Crystallization of an Undercooled Bulk Glass Forming Zr-Ti-Cu-Ni-Al Alloy

摘要

High vacuum, containerless, electrostatic levitation process has been used to study the undercooling and crystalliza- tion kinetics of a bulk glass forming Zr-Ti-Ni-Al alloy. The oxygen impurity level in the alloy has been found to play a crucial role in the crystallization kinetics of the undercooled melt. Overheating the melt above a critical threshold temperature results in enhancement subsequent undercooling. This crucial threshold temperature is found to be a func- tion of the overall oxygen content of the aloy direct measurement of the time-temperature-transformation (TTT) dia- gram for crystallization of the undercooled melt made following initial overheating above the threshold temperature show a strong dependence on overall oxygen concentration. An explanation of these observations is proposed.