Enhancements in the Bonding Properties of a Friction Stir Lap-Welded Interstitial Free Steel and Al Alloy by Introducing a Ni Interlayer

A pure Ni interlayer with a thickness of 0.1 mm was introduced between high-strength interstitial free steel and Al–Mg–Si alloy, which were friction stir lap welded, producing an excellent welded joint. The interface layer consisted γ-Ni solid solution, the mixed stirring zone contained alternate lamellae α-Fe solutions. addition strongly suppressed reaction Al Fe because atomic arrangement Ni. Furthermore, insertion depth pin has significant influence on Al/steel interfacial reaction. Under shallow depth, intermetallic compounds both FeAl Fe2Al5 observed at layer. maximum tensile-shear fracture load 4.3 kN achieved, fractures being present in substrate far away from weld.