Effect of carbon type and morphology on the microstructure and properties of carbon/copper composites

Abstract

Agglomerated brittle graphite and discontinuous matrix have decreased mechanics and friction properties of natural graphite/copper (NG/Cu) composites prepared through spark plasma sintering (SPS) with the blending of graphite and electrolytic copper powder. In that case, microstructure, mechanics and friction properties of NG/Cu composites were compared with that of carbon particles/cooper (CPs/Cu) composites prepared via ball-milling and SPS. CPs/Cu composites had higher strength and excellent friction properties, due to the uniform distribution of high content CPs (~4 μm, with carbon fiber structure) in Cu matrix, and ~36.40% of low angle grain boundaries (LAGBs) of continuous Cu matrix with finest grain size (~0.90 μm). The effective fixation of CPs by higher strength Cu matrix, combined with the consistency of microregion performance came from high-density uniformly dispersed of the micron-sized CPs, which significantly reduced the friction coefficient of the C/Cu composites against the steel disc and improved the stability of friction performance. Even at 400 °C, the softening of the matrix was greatly weakened owing to the pinning effect of CPs with excellent antioxidant properties on grain boundaries, and CPs/Cu composites still maintain good friction properties.