Oxygen impurity and microalloying effect in a Zr-based bulk metallic glass alloy

A Zr-base bulk metallic glass (BMG) alloy with the base composition Zr–10 at.%Al–5% Ti–17.9% Cu–14.6% Ni (BAM-11) was used to study the effects of oxygen impurities and microalloying on the microstructure and mechanical properties. Oxygen impurity at a level of 3000 appm dramatically reduced the glass forming ability and embrittled BAM-11 at room temperature. The embrittlement was due to the formation of oxygen-induced Zr₄Ni₂O nuclei that triggered near complete crystallization of the metallic glass. Microalloying with 0.1 at.%B+0.2%Si+0.1%Pb was effective in suppressing the crystalline phase formation and alleviating the detrimental effect of oxygen. Microstructural analyses indicate that the beneficial effect of the optimum dopants was mainly due to stabilization of the glass-phase matrix even though it contained high levels of oxygen. Thus, microalloying is effective in reducing the production cost and is very useful for manufacturing good-quality Zr-based BMGs from impure charge materials.