Deformation Microstructure and Chemical Composition of Surface Layers of Cu and Al under Friction in Lubricated Conditions

Friction and wear are accompanied by severe plastic deformation of surface layers similar to that observed under different processes of grain refinement. Recently, a dependence of tribological properties for four fcc metals (Ag, Cu, Ni, and Al) under friction in boundary lubrication was reported. A connection between friction and wear properties and stacking fault energy (SFE) of the studied metals was considered. Steady-state friction is mainly determined by deformation microstructure and chemical interaction in thin surface layers. The objectives of this work are to study the evolution of the microstructure with the depth of plastic deformation after friction of Al and Cu, to evaluate the effect of SFE on microstructure and wear loss, and to analyze the chemical composition of thin surface layers of Cu and Al and their correlation with the microstructure and wear properties of the studied metals. Friction surfaces were examined with a field emission scanning electron microscope. The cross-sectional TEM lamellae were prepared using focused ion beam. Evolution of deformation microstructure and chemistry of surface layers of Cu and Al after friction in the lubricant conditions were estimated by STEM, TEM, and XPS analyses.