Study on the Interfacial Structure and Thermal Conduction of Spark Plasma Sintering Diffusion‐Bonded Diamond/Cu Composites with Ni Interlayer

The diffusion‐bonded interface of diamond/Cu composites, with or without a Ni foil interlayer, is fabricated using the spark plasma sintering (SPS) diffusion bonding process. The shear strength and thermal conductivity of the diffusion‐bonded interface are tested, and their microstructure, element distribution, and fracture morphology are analyzed using an optical microscope, scanning electron microscope, energy‐dispersive spectrometer, and X‐ray diffractometer. The results show that the shear strength and thermal conductivity of the diffusion‐bonded interface of the diamond/Cu composite with the Ni foil interlayer increase by 23.29% and 58.98%, from 45.12 MPa and 347.73 W (m K) −1 to 55.63 MPa and 552.83 W (m K) −1 , respectively, compared to the interface without the Ni foil interlayer. The presence of the Ni foil interlayer significantly reduces the voids and holes at the diffusion‐bonded interface, with Ni diffusing to both sides of the interface. This diffusion leads to the formation of an α single‐phase CuNi solid solution with Cu and the production of the Ni 3 C phase with C. At the SPS diffusion‐bonded interface with the Ni foil interlayer, the extensive solubility of Ni in Cu and the formation of carbides greatly contribute to the improvement of thermal conduction across the interface.