Critical Shear Offset of Fracture in a Zr-based Metallic Glass

The nanoscale shear band operation process of Zr₅₅ Pd₁₀ Cu₂₀ Ni₅ Al₁₀ metallic glass (MG) was reined in by constant force during well-designed loading-holding-unloading cyclic microcompression test. Through the test, it is revealed that the whole shear banding process involves three stages: shear band initiation, shear sliding and shear band arrest. Based on the energy balance principle, the size-affected speed of shear sliding is interpreted. The energy originated from the shear sliding leads to heat-up of the shear plane; therefore, the temperature in shear band increases with the size of shear offset caused by the energy accumulation during shear sliding. Taking the glass transition temperature as the critical temperature of fracture for the Zr-based MG, the critical shear offset is predicted to be approximately 190 μm, fully in line with the experimental observation. This directly proved that the fracture of the MG is caused by the temperature rise during shear sliding.