Effect of structural relaxation on plastic flow in a Ni-Nb metallic glassy film

The effect of structural relaxation on the deformation behavior of Ni60Nb40 glassy films was systematically investigated. The film and Ti substrate were co-bent and morphology evolution of the film during bending was monitored. With a decrease in thickness there was a mode change from highly localized to non-localized deformation, with the critical thickness dependent on annealing temperature. During co-bending only a proportion of the stored elastic energy in the metallic glassy film can transfer to the shear band due to the presence of the Ti substrate, which increases with annealing temperature due to the decrease in interfacial adhesion between the film and the substrate. Thus the decrease in critical thickness and the thickness window for deformation mode change caused by annealing arises from the enhanced hardness/Young's modulus and the reduced interfacial adhesion. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.