Indentation size and loading strain rate dependent creep deformation of nanocrystalline Mo

Abstract

The creep behavior of nanocrystalline body-centered cubic Mo thin films was evaluated using nanoindentation testing. The creep rate and the corresponding strain rate sensitivity (m) were found to be strongly dependent upon indentation size and loading strain rate (LSR). Other than the mechanism of diffusion along indenter tip-sample interface previously proposed for face-centered cubic metals and metallic glasses, alternative mechanisms involving surface effect enhanced screw dislocation activities, inverse indentation size effect of hardness and LSR dependent microstructural and stress states, were proposed to interpret the observed dependence of penetration depth and LSR of m.