| Summary: | Heat input and high strain rate deformation during friction stir welding of aluminum and steel resulted in the diffusion-based formation of a FexAly intermetallic compound (IMC) layer. Compared with conventional friction stir welding tools, a friction stir scribe tool can reduce heat input significantly limiting the IMC layer thickness (~100–750 nm). Friction stir scribe joined lap joints fractured either through the welded interface or within the base aluminum alloy on the loading side, depending on IMC layer thickness during tensile lap shear testing. In addition, a modified effective heat of formation model predicted that Al13Fe4 formed first at aluminum/steel interface and, during welding process, was substituted by Al5Fe2 with local silicon enrichment, which was verified via microstructural characterization. Keywords: Friction stir scribe technology, Dissimilar, Intermetallic, Thermodynamic, Kinetic
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