<p>Friction welding has become a promising alternative to conventional fusion welding techniques for joining dissimilar materials like aluminum alloys and steel, particularly in the automotive industry. This study explores the microstructural evolution, elemental diffusion, and intermetallic compound (IMC) formation when A6061 aluminum alloy is friction-welded to ASTM A106 grade B steel using the friction welding tube to plate with external tool method. Friction welding was performed using a tungsten tool with a rotational speed of 1400&#xa0;rpm and a plunge depth of 1&#xa0;mm/min to achieve defect-free joints. Electron backscatter diffraction analysis revealed significant grain refinement at the joint interface, with dynamic recrystallization leading to the formation of high-angle grain boundaries. SEM–EDS line scan analysis confirmed the presence of FeAl intermetallic compounds, including Fe₄Al₁₃, Al₅Fe₂, Al₃Fe, and AlFe, with an intermetallic layer thickness ranging between 4.1 and 5.2&#xa0;µm. X-ray diffraction analysis validated the phase formations, showing distinct Fe and Al peaks on their respective sides, while the interface region exhibited intermetallic phases. The findings highlight that controlled IMC formation is crucial for ensuring a balance between joint strength and ductility. This study provides valuable insights into the microstructural characteristics of friction-welded dissimilar joints, contributing to advancements in lightweight structural applications where aluminum–steel joining is essential.</p>