Intermetallic Compound Layer Morphology and Distribution in Friction‐Welded Steel–Aluminum Components

In this study, the morphology, distribution, and local thickness of the intermetallic compound layer (IMC‐layer) in friction‐welded steel‐aluminum hybrid components used for Tailored Forming applications are investigated. By friction‐welding of steel and aluminum, which is the first step in the Tailored Forming process chain, an IMC‐layer in the joining zone is formed. In this study, the influence of friction‐welding parameters, such as rotational speed, friction pressure, friction length, upsetting pressure, and upsetting time, on local IMC‐layer thickness and distribution is examined. For characterization, a detailed analysis over the whole joining surface by means of scanning electron microscopy and a thorough statistical evaluation are employed. In the results, it is indicated that lower rotational speeds (700 rpm) in the friction phase result in more uniform and thinner IMC‐layer (<0.5 μm), while higher speeds (1600 rpm) produce a thicker and more heterogeneous IMC‐ layer (up to 0.9 μm). Tensile tests show that specimens with thinner mean IMC‐layer (0.17 μm) feature a higher tensile strength (244 MPa). The morphology and distribution of the IMC‐layer over the cross section of the friction‐welded specimen have a significant effect on the mechanical properties of the joint, with a uniform thin layer improving the tensile strength.