Low-temperature diffusion bonding of W/Mo joints with a thin Cu interlayer

By adding a thin Cu interlayer, refractory metals 93W and Mo1 can be reliably bonded by plasma activated sintering at low temperature. High resolution observations and an analysis of the joints indicate that the elements are sufficiently diffused at the interface of the W/Mo joints with a thin Cu interlayer without the formation of any intermetallic compounds. The maximum average shear strength of the W/Mo joint bonded at 700 °C for 20 min is greater than 210 MPa. Fe and Ni atoms in the 93 W alloy can diffuse into the thin Cu layer and form a Cu solid solution. The presence of Fe and Ni in the Cu solid solution promotes diffusion bonding at both the W/ thin Cu and thin Cu /Mo interfaces, which contributes to the high bonding strength of the W/Mo joint bonded at low bonding temperatures. The fracture model of the W/Mo joint bonded at 700 °C is a mixture of brittle fracture in the W base metal, ductile fracture in the thin Cu layer and brittle fracture in the Mo base material.