Mechanism Behind Al/Cu Interface Reaction: The Kinetics and Diffusion of Cu in Forming Different Intermetallic Compounds

The dissimilar welding of Al/Cu is widely used in power industry systems because it realizes satisfying mechanical and electrical properties with low cost. As the key factor influencing the property of welds, the formation of Al/Cu intermetallic compounds has attracted much attention. In this study, liquid–solid reaction between Al and Cu is realized at different temperatures, producing various intermetallic compounds (IMCs) which are mainly Al2Cu and AlCu. With morphology observation, the dependence of IMC formation on reaction temperature is determined. With the increase of reaction temperature, the thickness of Al2Cu keeps increasing while it finally reaches a stable state for AlCu IMC. Based on the diffusion theory, the inner formation mechanism of these IMCs is discussed. The formation of Al2Cu is controlled by the diffusion of Cu and Al in the melt, which is enhanced with high temperature. AlCu formation, on the other hand, is simultaneously affected by the diffusion of Cu and Al across the Al2Cu, which displays different kinetics.