Connection Reinforcement Design of W-Cu Joint: Transforming Immiscible Interface into Dual Reaction Diffusion Interface

Abstract

Weakly chemical bonding between dissimilar metals such as tungsten (W) and copper (Cu) due to the metallurgical incompatibility severely restricts the achievement of high strength. In this study, a dual interface reinforcement strategy was employed through introducing CrCoNi medium entropy alloy interlayer (W/MEA/Cu joint) with spark plasma sintering (SPS) technology. The largest tensile strength of ~256.7 MPa that is almost 171% higher than that of direct bonding (DB) joint can be achieved at the optimal bonding temperature of 1000 oC, which is associated with the transition of the joint from brittle fracture in DB joint to ductile fracture in W/MEA/Cu joint. Detailed multi-scaled microstructure and interface element diffusion behavior analyses reveal that solution strengthening matrix associated with the amorphous diffusion layer is formed at the interface between W and MEA through the reactive diffusion, whereas, mutual diffusion induced multiple phase structures in the interface between Cu and MEA result in the solid solution strengthening and precipitation strengthening, concurrently, leading to the interface bonding reinforcement. Our dual interface reinforcement methodprovides a good design strategy for improving the mechanical properties of immiscible metal materials.

Keywords: W-Cu joint, CrCoNi MEA, Element diffusion, Mechanical property, Strengthening mechanism