Failure analysis of an Al-Cu joint manufactured by eutectic diffusion bonding in evaporator tubes

Failure analysis of an Al-Cu joint manufactured by eutectic diffusion bonding in evaporator tubes was performed. The root cause of the failure was the high bonding temperature which is above the eutectic temperature of Al-Cu alloy by excessive applied current. Due to the high bonding temperature, the Al-Cu IMC was formed by which the pitting corrosion of Al tube in Al-Cu joint was accelerated. In addition, cavities were formed at the interface of Al-Cu joint. It is evident that bulge can be occurred by pressure of water freezing in the cavity. Simulation was used to confirm the possibility of bulge caused by the volume expansion of water freezing.