Nanoindentation investigation on creep behavior of amorphous Cu-Zr-AI/nano crystalline Cu nanolaminates

Berkovich nanoindentation experiments have been performed on amorphous /nanocrystalline nanolaminates with individual Cu-Zr-Al layers (45 nm, 90 nm, 225 nm) and Cu layers (7.5 nm & 15 nm). Elastic modulus, hardness and indentation morphology were detected and compared to those of single Cu-Zr-Al thin film. Creep deformation was systematically investigated at various holding depths and loading rates. For the sample with thinner amorphous layer, a more pronounced creep deformation was observed and it was confirmed to be due to the size effect of Cu-Zr-Al layers and the addition of Cu layers. The creep deformation was identified to be history-independent through applying various loading rates. The strain rate sensitivities were calculated from the steady-state creep and a sharp enlargement appeared as the amorphous layer reduced down to 90 nm, implying a transition of creep mechanism in nanolaminates. (C) 2017 Elsevier B.V. All rights reserved.