Tensile stress-strain response of metallic glass matrix composites reinforced with crystalline dendrites: Role of dendrite morphology

Bulk metallic glass composites (BMGCs) consisting of soft crystalline phases (commonly referred to as dendrites) in a metallic glass matrix have shown enhanced tensile ductility compared to conventional bulk metallic glasses (BMGs). Experiments and atomistic simulations suggest that a large number of geometrical parameters such as aspect ratio, spacing and orientation of dendrites as well as their spatial distribution can affect the mechanical response of BMGCs. However, the precise mechanism by which these parameters influence shear band initiation and propagation is not well understood. Therefore, continuum simulations of tensile loading on BMGCs with different morphologies are performed in this work. The results show that aspect ratio of dendrites has weak effect on the mechanical response up to the peak stress stage. However, it influences ductility considerably, albeit in a different manner for BMGCs with high and low hardening dendrites. The present analysis suggests that a BMGC capable of displaying mildly strain hardening response with large strain to failure can be designed by using closely spaced dendrites of high aspect ratio, and aligning them parallel to the maximum tensile stress direction.