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Effect of post-weld heat treatment on inhomogeneity of aluminum/copper rotary friction welded joint

The inhomogeneity of AA1060 aluminum and T2 copper friction welded joint was investigated through comparing the microstructure and properties at center, 1/2 R and edge positions along the radius. Sound joining was achieved at the center position of as-welded joint which fractured in the aluminum base metal, and the tensile strength decreased gradually from the center to the edge position, while the electrical resistivity increased. After heat-treated at 100 °C for 2 h, the joint had the highest integral tensile strength and the lowest electrical resistivity. When the joint was heat-treated at temperature above 400 °C, cracks formed in the interface and deteriorated the properties of joint. Part of intermetallic compounds layer in the center position of joint heat-treated at 400 °C disappeared. With increasing the heat treatment temperature or time, the disappearance of intermetallic compounds extended from the center to 1/2 R position. Al4Cu9 phase grew faster than Al2Cu and AlCu phases. The growth rates of Al2Cu, AlCu and Al4Cu9 phases were the fastest at the edge position and the slowest at the 1/2 R position. The activation energy of Al2Cu, AlCu, Al4Cu9 phases and total intermetallic compounds were 92.24 kJ mol−1, 55.59 kJ mol−1, 146.92 kJ mol−1 and 121.40 kJ mol−1, respectively.