Evolution of shear bands and its correlation with mechanical response of a ductile Zr55Pd10Cu20Ni5Al10 bulk metallic glass

The correlation between three-dimensional spatial evolution of shear bands and mechanical response of a ductile Zr55Pd10Cu20Ni5Al10 bulk metallic glass (BMG) was investigated by an interrupted compression technique combining with systematic scanning electron microscope observations. It was found that the formation of shear bands is determined primarily by the inherent material behavior whereas the external factors, such as surface imperfections, impose only minor influence. At the early stage of plastic deformation, the serration events were discovered to arise from coupled operation of multiple shear bands. The shear band operation takes place in a progressive manner. The resistance for shear band propagation appears to be higher than that for their initiation, leading to an apparent strain-hardening during the transition from elastic deformation to steady plastic flow. The plasticity of BMGs depends on the competition between the formation of new shear bands and the reactivation of primary shear bands during plastic deformation and large plastic strain of ductile BMGs is mainly accomplished by the formation of new shear bands. This study provides comprehensive observations on the low-temperature deformation process of BMGs for understanding the mechanical properties of glassy alloys.