Microstructure and thermo-physical properties of Cu Ti double-layer coated diamond/Cu composites fabricated by spark plasma sintering

Diamond/Cu composites were fabricated by spark plasma sintering (SPS) process with CuTi double-layer coated on the surface of diamond particles as the reinforcement phase. The effect of sintering temperature, pressure and holding time on the microstructure and thermo-physical properties of the composites were investigated. The results showed that the interface between diamond and copper matrix were tightly bonded with the increase of sintering temperature, the fracture surface morphologies were consisted of ductile fracture on copper matrix and diamond particles falling out from the bonding interface. As the double-layer coated on the surface of diamond particles made the interface present tightly bonding, which improved the interfacial bonding between diamond and copper matrix. It was found that the temperature, pressure and holding time together can accelerate the densification process and further improve the thermo-physical of the composites. Comprehensive consideration of process parameters, the process parameters conducive to strengthening the interface bonding are 900 °C, 60 MPa and 40 min, and the relative density, bending strength, hardness and thermal conductivity of CuTi double-layer coated diamond/Cu composites were 99.77%, 153.52 MPa, 148.63 HV and 258.04 W/m·K, respectively. Moreover, higher sintering temperature, larger pressure and longer holding time could cause copper matrix to melt and grain growth as well as the graphitization of diamond, which reduced the densification and lowered the thermo-physical of the composites.