Microstructure in interface zone of diffusion welded joint of Mo and Cu

In this paper, Mo and Cu were welded together by diffusion welding with or without a Ni interlayer. SEM, EDS, EPMA, XRD were used to characterize the structure and the element distribution of the interface zone. The results showed that the Mo/Cu joint combined homogeneously by diffusion welding, the diffusion layer formed at the interface due to Mo atoms and Cu atoms inter-diffusion. There were some micro-voids on the copper side of the joint due to the role of kirkendall effect, and the voids reduced the performance of the joint. For the Mo/Ni/Cu joint, Mo/Ni and Ni/Cu interface were linked together, and the tensile strength of the Mo/Ni/Cu joint was higher than the Mo/Cu joint, because the added nickel eased the thermal stress of the joint. A solid solution was formed at the Mo/Ni interface where a joint brittle fracture took place.