Deformation mechanism map of Cu/Nb nanoscale metallic multilayers as a function of temperature and layer thickness

TL;DR

This study maps the deformation mechanisms of Cu/Nb nanoscale multilayers across different temperatures and layer thicknesses, revealing a transition from dislocation glide to interface diffusion-controlled deformation.

Contribution

It introduces a deformation mechanism map for Cu/Nb multilayers, highlighting the temperature and thickness-dependent transition in deformation behavior.

Findings

Dislocation glide dominates at larger layer thicknesses and room temperature.

Interface-related mechanisms are active at thinner layers at room temperature.

Diffusion-controlled deformation occurs at high temperatures and small layer thicknesses.

Abstract

The mechanical properties and deformation mechanisms of Cu/Nb nanoscale metallic multilayers (NMMs) manufactured by accumulative roll bonding (ARB) are studied at 25C and 400C. Cu/Nb NMMs with individual layer thicknesses between 7 and 63 nm were tested by in-situ micropillar compression inside a scanning electron microscope Yield strength, strain-rate sensitivities and activation volumes were obtained from the pillar compression tests. The deformed micropillars were examined under scanning and transmission electron microscopy in order to examine the deformation mechanisms active for different layer thicknesses and temperatures. The analysis suggests that room temperature deformation was determined by dislocation glide at larger layer thicknesses and interface-related mechanisms at the thinner layer thicknesses. The high temperature compression tests, in contrast, revealed superior thermo-mechanical stability and strength retention for the NMMs with larger layer thicknesses with deformation controlled by dislocation glide. A remarkable transition in deformation mechanism occurred as the layer thickness decreased, to a deformation response controlled by diffusion processes along the interfaces, which resulted in temperature-induced softening. A deformation mechanism map, in terms of layer thickness and temperature, is proposed from the results obtained in this investigation.