Abstract:A layer of Cu was sintered on the surface of Al₂O₃ ceramic before bonding, and then diffusion bonding technology was applied to bond Al₂O₃/Cu to Al alloy. SEM and EDS were applied to analyze the interfacial microstructures of Al₂O₃/Cu/Al joint. The preliminary research shows that Al/Cu interfacial microstructures are the main factor affecting joint strength. With increasing bonding temperature and time, ((Al)+θ) mixture separates out from Al alloy, and (Cu)+ γ₁）mixture separates out from Cu layer. The two kinds of mixtures develop first along interface, then (Cu)+γ₁) microstructure turns progressively into (ξ₂ +δ) with bonding temperature and time prolonged. At the same time, ((Al)+θ) and /(ξ₂ +δ) phases move gradually into base materials. The two kinds of changes result in reducing bonding strength greatly. The optimum diffusion bonding parameters are determined as follows: T=773K, t=1226s and p=6MPa, at which the tensile strength of the joint is 108MPa, and the shear strength of the joint is 45MPa.

Key words: Al alloy; Al₂O₃ ceramic; diffusion bonding