Microstructure and tribological behavior of interfaces in Cu-SiO2 and Cu-Cr metal matrix composites

In this work, Cu-SiO2 and Cu-Cr metal matrix composites were fabricated by the powder metallurgy method. The morphologies, microstructures and tribological behaviors of the Cu-SiO2 and Cu-Cr interfaces were studied. The results indicated that the amorphous SiO2 in the vicinity of the Cu-SiO2 interface was transformed into cristobalite crystal after sintering. The interfaces of the fcc-Cu and cristobalite SiO2 were mostly incoherent interfaces. The Cu-Cr interface consisted of an interlaced bcc-Cr-rich multiphase and some microvoids. These microvoids were generated from the clustering of the vacancies resulting from the asymmetric mutual diffusion of Cu and Cr atoms. The vacancies present in the Cu-Cr interface provided an abundance of fast-diffusion channels for the O atoms, resulting in the presence of the Cr2O3 nanoparticles in the vicinity of the microvoids. The Cr2O3 nanoparticles enhanced the mechanical properties of the interface via the dispersion strengthening mechanism. When the indenter slid through the Cu-SiO2 and Cu-Cr interfaces, the penetration depth increased rapidly, and the friction coefficient first decreased and then rapidly increased. Both the Cu-SiO2 and Cu-Cr interfaces were easily broken during the sliding test. The interfaces were broken more severely at the higher load, thereby reducing the rate of the change in the penetration depth and friction coefficient during their dynamic damage process. •Linking the morphologies, microstructures and tribological behaviors of the Cu-SiO2 and Cu-Cr interfaces.•The transformation mechanisms of the Cu-SiO2 and Cu-Cr interfaces were discussed from the view of the kinetics and thermodynamics.•Both the Cu-SiO2 and Cu-Cr interfaces were easily broken during the sliding test due to the weak bonding interface.