Wear mechanism transition dominated by subsurface recrystallization structure in Cu–Al alloys

Abstract

Dry sliding tribological properties and worn subsurface microstructures were investigated in Cu–Al alloys with Al concentrations of 0–2.2wt%. It was found that the wear volume of Cu–Al alloys decreases with an increasing Al content below 0.5wt%, and increases at higher Al contents above 0.5wt%. For each sample, a worn subsurface layer is generated consisting of dynamic recrystallization (DRX) structures beneath the top nanostructured mixing layer (NML). DRX grain sizes decrease monotonically with an increasing Al content. As the DRX grain sizes are larger than 0.7μm, the wear-off process is dominated by cracking and peel-off of the NML. For the samples with finer DRX grains, cracking takes place within the DRX layer, of which peeling-off becomes a dominant mechanism. Such a wear mechanism transition is in agreement with the quantitative correspondence between wear volume and DRX grain size, indicating that the minimum wear volume (i.e., the maximum wear resistance) exists at an average DRX grain size of about 0.7μm.