Joining Dissimilar Mg/Al Alloys by Solid-State Friction Spot Welding

To reduce intermetallic compounds (IMCs), dissimilar Mg/Al alloys were joined by solid-state friction spot welding. No incomplete refilling was observed when Al sheet served as the upper sheet. Almost no IMCs formed at the sleeve-affected zone even though the sleeve plunged during welding. A 530-mu m-thick Al12Mg17 layer formed at the center of the Al/Mg joint due to a large amount of liquid phase formed during welding. Only a 5-mu m-thick Al3Mg2 layer formed in the Mg/Al joint because the oxide film on the Al sheet was difficult to break. The Al/Mg joint exhibited much higher lap shear failure load even though it had a thicker IMC layer. The joint formation mechanism was studied.