Numerical investigation of tensile response of notched bulk metallic glass composite specimens

In this work, plane strain finite element and atomistic simulations of tensile response of double edge notched bulk metallic glass composite (BMGC) samples are conducted. A special constitutive model is used to represent the response of the bulk metallic glass matrix along with J flow theory of plasticity to characterize the crystalline dendrites in the former, while a CuZr based glass matrix containing single crystal Cu dendrites is modeled in the latter. It is found that the ratio of notch root radius to the distance between the notch tip and the nearest dendrite, R/l, is an important parameter that governs the plastic deformation behavior and possible failure mechanisms. Both finite element and atomistic analyses show that as R/l increases from a small to moderate value, a transition occurs in plastic flow through multiple shear banding with deflection by dendrites to ligament necking. On further increase in the above notch acuity parameter, the deformation behavior again changes to multiple shear banding without much hindrance from dendrites. Specimens with moderately blunt notches (as characterized by the value of R/l) having high hardening elongated dendrites exhibit pronounced plastic deformation along the ligament resulting in necking. The influence of BMGC microstructure and hardening of dendrites is also investigated from the finite element analyses.