Deformation kinetics in Zr-based bulk metallic glasses and its dependence on temperature and strain-rate sensitivity

摘要

Micromechanical analysis of ductile bulk metallic glasses at various temperatures and strain rates revealed accurate information on inhomogeneous flow kinetics. The disappearance of flow instabilities (i.e. serrations) at low temperatures correlates with a change from negative to positive strain-rate sensitivity and exhibits an activation energy of 0.37 eV. Based on these findings, a constitutive deformation model for thermally-activated flow in disordered systems is presented, which accounts for possible structural relaxation processes within the shear bands. Similarities in the flow behaviour of bulk metallic glasses with the Portevin-Le Chatelier effect known for crystalline metals are discussed.