The Hybrid Friction Surfacing Deposition Assisted Arc Welding (FsaAW) Approach for Dissimilar Steel/Al Joining of Automobile Structure

A multi-material design strategy of steel and aluminium alloy is a key solution in response to stringent emission requirements and to offset the additional weight of batteries in electric vehicles. However, dissimilar Al/steel welding is mainly challenging due to the formation of brittle and hard intermetallic compounds (IMC). In order to resolve the issue of IMC formation, the present study proposed an alternative manufacturing method consisting of friction surfacing deposition and arc welding. The proposed method involves two steps for dissimilar welding: step 1, friction surfacing deposition of aluminium alloy on the steel surface and step 2, arc welding of friction surfacing deposited steel and aluminium alloy. Auxiliary friction surfacing deposition acts as a preliminary bonding and avoids the direct contact between steel and aluminium alloy during arc welding, which eludes the IMC formation at the interface. 3.15 mm thick E46 steel and 3 mm AA6061-T6 were selected as base metals to investigate the feasibility of the proposed method. The welded joints were characterized by microstructure, microhardness, and lap-shear tests. Compared to conventional arc welding, the proposed method provides better mechanical performance. Additionally, the proposed method can also be applicable to other mutually insoluble dissimilar combinations.