In situ isothermal crystallisation of Zr₄₈Cu₃₆Al ₈Ag₈ bulk metallic glass based on pair distribution function analyses

In situ synchrotron X-ray measurements were performed on the isothermal annealed Zr₄₈Cu₃₆Al₈Ag₈ bulk metallic glass (BMG). The crystallisation behaviour and structural evolution during the isothermal annealing were investigated by pair distribution function (PDF) analyses. The results indicate that the crystallization behaviour of the samples annealing at 743 K can be well described by the PDF data. The crystallisation process starts from 12 min and finishes at 54 min, with a rapid transforming period within 24-42 min. Dramatic structural changes take place in short, medium and long atomic range during crystallization. It is found that atoms closely pack in short range, while loosely pack in medium range, indicating the short and medium range ordering in BMG. Furthermore, atoms pack more and more closely during crystallisation process, and finally form the closely packing shells.