Effect of Ni content in Cu_{1- x}Ni_x coating on microstructure evolution and mechanical properties of W/Mo joint via low-temperature diffusion bonding

The 93W and Mo1 refractory metals were bonded with different Cu_{1- x}Ni_x coating interlayers of various Ni content using plasma-activated sintering at 700 °C. The effects of the Ni content in the Cu_{1- x}Ni_x coating interlayer on the interfacial microstructure evolution and mechanical properties of the W/Mo joints were studied. The maximum average shear strength of the W/Mo joint was 316.5 MPa when the Ni content of the Cu_{1- x}Ni_x coating interlayer was 25 %. When the Ni content of the Cu_{1- x}Ni_x coating interlayer was below 50 %, the atomic diffusion at the W/Mo joint interface was adequate without the formation of intermetallic compounds, as demonstrated by the High Resolution Transmission Electron Microscope analyses of the joints. The presence of Ni in Cu_{1- x}Ni_x promoted diffusion bonding at the interface, which contributed to the high mechanical properties of the W/Mo joint. With an increase in the Ni content of the Cu_{1- x}Ni_x coating interlayer, the MoNi intermetallic compound (IMC) nucleated and grew at the Cu_{1- x}Ni_x coating/Mo1 interface. When the Ni content of the Cu_{1- x}Ni_x coating interlayer was above 50 %, the generation of a brittle MoNi IMC weakened the shear strength of the W/Mo joint dramatically.