Shear band velocity and activation volume during shear deformation by acoustic emission in a Zr-based bulk metallic glass

An analysis is presented for the shear band velocity of plastic deformation and activation volume of the shear transformation zone (STZ) in a Zr60Cu30Al10 bulk metallic glass (BMG). Compared to the values calculated by the stick-slip model, the values of shear band velocity calculated after optimization by the acoustic emission technique are much larger than those reported previously. Plastic flow in BMGs is found to be described by a powerlaw correlation between the maximum velocity of the shear band and the strain rates. Combining the free volume theory and the STZ theory, the relationship between the volume change in the STZ and the shear band velocity is derived as omega = A(27 - lnv /l). The value of A, which is a material dependent constant, is 5.43 x 10-3 for the current BMG at room temperature.