Preliminary Investigation of Friction Stir Welding Aluminium/Copper Lap Joints

An investigation has been made of the feasibility of friction stir welding of dissimilar lap joint of an aluminium plate to a copper plate, which is difficult to weld by fusion welding methods because of the formation of brittle intermetallic compounds (IMC). Although the level of bond strength was quite low, it exhibited a general tendency to increase with a rise in rotation speed. Various microstructures with different morphologies and properties were observed in the stirred zone of aluminium and Al/Cu interfacial region. Comparison of the fracture location with the microstructure suggests that IMC formed in the interfacial region was responsible for the low strength of the joints. X-ray diffraction from the fracture surfaces indicate that Al4Cu9, AlCu, and Al2Cu were the main intermetallic compounds formed in the interfacial region. The performance of the joints was improved significantly by using Zn intermediate layer between Al and Cu owing to limiting the formation of the harmful intermetallic compounds and distributing them over wider areas.