Quasi-static and dynamic deformation behavior of Hf28Be18Ti17Zr17Cu7.5Ni12.5 high-entropy bulk metallic glass

A series of quasi-static and dynamic compression experiments were performed on Hf28Be18Ti17Zr17Cu7.5Ni12.5 high-entropy bulk metallic glass (HE-BMG) at room temperature and at different strain rates. The findings showed that under quasi-static loading, strain rate had no considerable impact on the fracture strength of the HE-BMG. Nevertheless, the plastic strain disappeared with the increasing strain rate. The analysis of the fracture morphology under quasi-static loading revealed the shear fracture mode of HE-BMG and the critical role of the shear bands in the plastic deformation stage. In addition, the dynamic mechanical properties of the HE-BMG were tested at different strain rates. The dynamic deformation behavior of the HE-BMG was also investigated using a split Hopkinson pressure bar. Compared with the quasi-static compression results, a strain-rate softening phenomenon was observed under dynamic loading. With the increasing strain rate, the yield strength of the HE-BMG gradually decreased, and three different failure modes occurred under dynamic loading. The reasons for the different fracture mechanisms were also investigated by examining the unique fracture surface morphology of the HE-BMG specimens in dynamic compression.