Fabrication of copper–diamond composite by friction stir processing

The friction stir process has been used for the first time to fabricate copper–diamond composite. The initial diamond particles were fragmented and embedded into Cu alloy due to the pressures applied during the friction stir process. A drastic refinement of the diamond particles was observed due to attrition during processing. Chromium (Cr) particles in the base Cu alloy have also been refined during friction stir process which appears to further promote grain refinement in Cu. The Cu–diamond interface appears to have good adhesion, except at chipped corners of some particles. The Cr particles decorate the Cu–diamond interface indicating a strong affinity of Cr to the diamond surface. Also, the adhesion of Cr particles is better on the surface of smaller fragmented diamond particles. The thermal conductivity of the composite is lower than friction stir-processed copper and as-received copper alloy due to significant grain refinement and the presence of Cu–diamond interfaces. However, the fabricated composite may find potential uses in commercial applications due to the unique combination of increased hardness and high thermal conductivity.