Temperature dependence of shear transformation zone volume and plasticity in bulk metallic glass

In this paper, a theoretical formulation for shear transformation zone (STZ) volume, shear band density, and plasticity are presented and temperature dependence of these parameters are discussed. In particular, the strain energy barrier for a shear cooperative transformation is modeled following the Johnson and Samwer approach for amorphous metallic glasses; positive temperature dependence of the STZ volume and negative temperature dependence of the shear band density are formulated, based on which a significant improvement in plasticity at lower temperatures is predicted. Experimental data on the plasticity for Vit105 bulk metallic glass - obtained from the present compression tests and also from the literature - show negative temperature dependence, which is consistent with the prediction of the analytical formulation.