Dynamic properties of major shear bands in Zr–Cu–Al bulk metallic glasses

Abstract We present a systematic investigation of shear-band dynamics as a function of chemical composition in the ZrxCu90−xAl10 (x = 45–65) metallic glass system. We investigate aging dynamics in the non-serrated flow regime, shear-band velocities in the serrated flow regime, the transition between these two flow modes, and the transition from ductile to brittle behavior. We find that the activation energy for shear-band propagation is largely determined by the underlying time scales of the shear process, and that temperature-dependent stress drops only play a minor role. The activation energy as a function of composition can be linked to the bonding strength between the fastest diffusor, Cu, and its coordinating atoms, represented by the ratio of strong Cu–Zr to weaker Cu–Cu bonds. This indicates that the resistance to accelerated shear, i.e. the apparent activation barrier, is primarily controlled by a chemical nearest-neighbor effect.