Strain-rate-dependent deformation behavior in a Ti-based bulk metallic glass composite upon dynamic deformation

The deformation behavior of in-situ Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅ bulk-metallic-glass (BMG) composites was investigated upon dynamic deformation. The present BMG composite exhibits good dynamic mechanical properties, combining high fracture strength (1850 MPa) with remarkable plasticity (>10%) at the strain rate of 1.3 × 10³ s^-1. Ductile to brittle transition occurs with the increase of strain rates, which can be ascribed to the deteriorated ability of dendrites to impede the propagation of shear bands at higher strain rates. An obvious positive to negative transition on strain rate dependence of flow stresses can be observed with the increasing strain rates. Detailed analysis reveals that the variation from the dendrite-dominated mechanism associated with dislocation movement to the matrix-dominated fracture related to thermal softening is responsible for the present transition. The constitutive equations based on their deformation mechanisms are established for describing the present transition.