Dependence of ductility on free volume in a Cu-Zr-based metallic glass

Cu₄₆Zr₄₇al₇ bulk metallic glass (BMG) alloys with different free volume states were obtained through thermal treatments such as annealing and quenching. It was demonstrated that the ductility of BMGs was closely related to the free volume and the ductility of thermally embrittled BMGs can be restored by thermal treatments. XRD patterns confirm amorphous structure of the annealed and quenched alloy, while no nanocrystallization or nanometer-sized phase separation is detected. It is found that the ductility of thermally embrittled annealed sample can be partially recovered by quenching process, as the quenched sample present much better plastic deflection than the annealed sample. The fracture surface appearance in the embrittled annealed samples is on a much finer scale than that for the ductile cast samples.