Microstructural characterization and mechanical properties of micro friction stir welded dissimilar Al/Cu ultra-thin sheets

In this study, dissimilar butt joints of 1.0 mm thick 6061-T6 aluminum alloy and T2 pure copper ultra-thin sheets were fabricated using micro friction stir welding under various tool traverse speeds while the rotational speed was 3000 rpm. The results indicated that the reliable metallurgical bonding was achieved at Al/Cu interface, which can be attributed to the formation of continuous Al2Cu-AlCu-Al4Cu9 intermetallic compounds (IMCs) layer. A large portion of Cu particles consisting of pure Cu and Al/Cu IMCs were dispersed in the Al matrix and promoted the formation of the composite-like structure. Furthermore, lamellar structure was produced adjacent to the Al/Cu interface. The higher hardness was measured in the nugget zone where a few IMCs were fabricated. The thickness of the interfacial IMCs layer played a significantly role in determining the weld tensile strengths, and the maximum tensile strength of 236.2 MPa (equivalent to 82.9 % of Cu base metal) was obtained, which fractured in the heat affected zone on the aluminum side.