A failure mechanism based constitutive model for bulk metallic glass

The formation of micro-cracks caused by the nucleation and coalescence of nano-voids in the shear bands is regarded as a main failure mechanism of bulk metallic glasses (BMGs). Based on such a failure mechanism and the free volume theory, a 3-D constitutive model of BMGs is developed in this work within the framework of continuum mechanics; and the concentration of nano-voids in the BMG is introduced into the constitutive model as an internal variable whose evolution characterizes the nucleation and coalescence of nano-voids during the deformation. Moreover, to describe both the brittle and ductile failure modes presented during the tensile and compressive deformations of BMGs, respectively, a failure criterion is established by introducing a stress triaxiality, which can describe the failure characteristics of BMGs under different stress states. Finally, through the finite element implementation of the developed constitutive model, the effectiveness of the model is validated by comparing the simulated results with the experimental ones of BMGs; in addition, the nucleation and coalescence of nano-voids in the BMGs during the tensile and compressive deformations are also predicted, and the comparison of predicted results and experimental ones demonstrates the reasonability of the developed model.