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 of a γ-Ni solid solution, and the mixed stirring zone contained alternate lamellae of γ-Ni and α-Fe solid solutions. The addition of a Ni interlayer strongly suppressed the reaction between Al and Fe because of the atomic arrangement of Ni. Furthermore, the insertion depth of the stirring pin has a significant influence on the Al/steel interfacial reaction. Under shallow insertion depth, the intermetallic compounds of both FeAl and Fe2Al5 were observed at the interface layer. A maximum tensile-shear fracture load of 4.3 kN was achieved, with fractures being present in the steel substrate far away from the Al/steel weld.

Friction welding of high Cr white cast iron to AISI 1030 steel with Ni interlayer

In this study, the effect of friction time on microstructure and weldability of AISI 1030 steel with nickel interlayer and high chromium white cast iron welded by the friction welding method were investigated experimentally. The weld joints were produced with 2000 rpm rotational speed, under 80 MPa friction pressure, 150 MPa forging pressure, for 8 s forging time and 8, 10 and 12 s friction times. After the friction welding process, the microstructures of the weld interfaces were analyzed by optical microscopy, scanning electron microscopy, energy dispersive spectrometry, elemental mapping and X-ray diffraction analysis. The results were lateron compared theoretically and experimentally. The increasing friction time led to high frictional heat input. The results indicated that friction time plays a vital role on the microstructure and weldability.