Direct measurements of shear band propagation in metallic glasses – An overview

A series of experimental efforts have recently made in an attempt to gain understanding of shear band propagation in metallic glasses. It was found that plastic flow serration observed in compression was actually caused by successive (intermittent) shear along a single shear plane, not random shear band emission. Several experimental techniques, including conventional Instron, attaching linear voltage differential transducer, strain gage, and high-speed camera, were employed to investigate shear band propagation during flow serration. The test results showed that the shear band propagation consisted of the acceleration, deceleration, and the final arrest. The maximum velocity of a propagating shear band was about 4 mm s−1, which corresponds to a high strain rate of about 105 s−1. The viscosity of a propagating shear band was evaluated to be only about 1 × 104–5 × 105 Pa s, indicating the shear band was very fluidic. Video images capture from a high-speed camera also revealed that the shear was simultaneous, rather than in a progressive fashion.