Interfacial quality prediction model for Al/steel sheets during friction stir–assisted double-sided incremental forming with synchronous bonding

The widely investigated Al/steel laminated structures are challenged with subsequent plastic deformation due to the prone generation of interfacial brittle intermetallic compound layer. To overcome this drawback, a recently proposed thermomechanical forming technology as friction stir–assisted double-sided incremental plastic forming with synchronous solid-state interfacial bonding is utilized to fabricate Al/steel laminated structures. Typical interfacial bonding-forming performances produced by a series of experiments classified as sound bonding, de-bonding, over-thinning, penetration and crack are individually assessed. Local working peak temperature and maximum forming force in loading area are recorded and evaluated during stable bonding-forming stage. Considering the heat-force coupling effect, a pressure-strain-temperature–based prediction model is modified to assess interfacial quality, which is conformed to experimental results. This work can help obtain proper process window to successfully fabricate Al/steel laminated parts and shall also inspire to build guidance of related thermomechanical joining-with-forming processes to achieve high interfacial performance.