Abstract: Developing ductile bulk metallic glasses (BMGs) can benefit from an in-depth understanding of the structure-property relation during plastic deformation. However, endowing BMGs with tensile ductility in BMGs needs to reveal the response of critical structure units during deformation. Here, we report the experimental results of an in-situ synchrotron high-energy X-ray study of a Zr-based BMG under uniaxial tension after preprocessing by canning compression of the three-dimensional compressive stress state. It is revealed that the canning-compressed BMG (CC-BMG) sample has better tensile ductility and higher ultimate strength than the as-cast sample, which possesses heterogeneous and loosely packed local structures on medium-range scales. The experimental results revealed two stages of plastic deformation in the CC-BMGs compared with one stage of plastic deformation in the as-cast BMG. Moreover, the shift in the first sharp diffraction peak along the tension direction for the canning-compressed sample is substantially more pronounced than that of the as-cast sample. Furthermore, the real-space analysis illustrates a competition mechanism between the 2-atom and 3-atom connection modes on medium-range order during the plastic deformation of the CC-BMG. Additionally, the ordering on the medium-range scale decreases in the first plastic deformation stage but increases in the second plastic deformation stage. Therefore, a structural crossover phenomenon occurs in the CC-BMG during plastic deformation. Our results demonstrate a structure-property correlation for the CC-BMGs of heterogeneous medium-range ordered structures, which may be beneficial for endowing BMGs with ductility based on medium-range order engineering techniques.

Key words: Bulk metallic glass, Medium-range order, Tensile ductility, Structure-property relation