In Situ Observation of Diffusion Behavior and Microstructural Evolution on Interfaces in Al/Cu Bimetal

Synchrotron X-ray radiography was used to in situ study the diffusion behavior and microstructural evolution of Al/Cu bimetal. The interface diffusion, dendritic/eutectic growth and the formation of intermetallic compounds around the Al/Cu bimetal interface were analyzed. During the isothermal diffusion process, a liquefied transition zone at the interface with a concentration gradient was formed when the Cu concentration exceeded eutectic composition of Al-Cu alloy. During the solidification of transition zone, the growth sequence of α-Al dendrites and eutectic structure were mainly dominated by the variation of Cu concentration and thermal field according to the temperature of the liquidus line of the equilibrium phase diagram. Finally, the transition zone around the interface were identified to be I (α-Al), II (Al+Al2Cu), III (Al2Cu) and IV (Al2Cu, AlCu and Al4Cu9), respectively.