Effect of friction stir welding parameters on the microstructure and mechanical properties of the dissimilar Al–Cu joints

Butt joints of 1060 aluminum alloy and commercially pure copper were produced by friction stir welding (FSW) and the effect of welding parameters on surface morphology, interface microstructure and mechanical properties was investigated. The experimental results revealed that sound defect-free joints could be obtained under larger pin offsets when the hard Cu plate was fixed at the advancing side. Good tensile properties were achieved at higher rotation rates and proper pin offsets of 2 and 2.5 mm; further, the joint produced at 600 rpm with a pin offset of 2 mm could be bended to 180° without fracture. The mechanical properties of the FSW Al–Cu joints were related closely to the interface microstructure between the Al matrix and Cu bulk. A thin, uniform and continuous intermetallic compound (IMC) layer at the Al–Cu butted interface was necessary for achieving sound FSW Al–Cu joints. Stacking layered structure developed at the Al–Cu interface under higher rotation rates, and crack initiated easily in this case, resulting in the poor mechanical properties.