Age-hardening in a two component immiscible nanolaminate metal system

Abstract

Density functional theory was used to predict the diffusion and precipitation of Cr in Cu. The energy barrier of Cr diffusion in Cu is comparable to the self-diffusion of Cr, and higher than the energy barrier of Cu self-diffusion. The simulations support the experimentally measured hardness of 30nm thick nanolaminate layers of Cr/Cu-3.4%Cr. As-deposited films had a hardness of 6.25 GPa; annealing at 373K decreased hardness to 5.95 GPa, while annealing at 573K increased the hardness to 6.6 GPa. Transmission electron microscopy indicates there is significant local strain due to precipitation, in agreement with theoretical predictions.