Thermal shock behavior of W–Cu function graded material/CuCrZr joints fabricated by hot isostatic pressing

In this study, W-Cu functionally graded material/CuCrZr alloy (W-Cu FGM/CuCrZr) joints was successfully bonded by hot isostatic pressing (HIP). The effects of bonding temperature (850-1000 °C) on the microstructure, mechanical properties and thermal conductivity of the joints were systematically investigated. In addition, their damage behavior under thermal shock cycling between 800 °C and room temperature was evaluated. The results indicate that increasing the bonding temperature significantly promotes the bonding strength and thermal conductivity of the joint. The joint fabricated at 1000 °C exhibited the optimal performance with a shear strength of 204.4 MPa and a thermal conductivity of 264.6 W/(m·K). Thermal shock testing reveals that cracks initiate at the W/CuCrZr interface due to the coefficient of thermal expansion mismatch between the W-Cu FGM and CuCrZr, as well as the extrusion of Cu under cyclic thermal stress. With increasing numbers of thermal shock cycles, these cracks then propagate along W/Cu interfaces and the fatigue CuCrZr matrix, hereby accelerating interfacial damage and leading to a marked decrease in shear strength.