Temperature evolution, IMC formation, and resulting bonding efficacy in bimetallic tubular components fabricated by a novel friction stir backward extrusion cladding method

The ability to economically offer distinct properties within a single component has gathered significant attention for bimetallic or cladded tubular components across various industries. A novel friction stir-based cladding method and its in-depth analyses to achieve internal cladding of Al inside the stainless steel (SS) tubes are presented. The process outcome with the variation in process parameters and its impact on heat generation and intermetallic compounds (IMCs) formation was analyzed. In this process, the joining between the base substrate and the cladded material is due to the heat generation that leads to interdiffusion and ultimately promotes the formation of IMCs. The mechanism of IMCs formation, its growth phenomenon, and its impact on joining efficacy were investigated. The cladded Al exhibited an approximately twofold increase in grain size compared to the base Al alloy, as revealed through electron back-scattered diffraction (EBSD) analysis. The coarser grains help to restrict the propagation of fracture during the flattening test. The cladded tube exhibits no sign of delamination after compression, which paves the way for the industrial adoption of the process.