Single point incremental forming of Cu-Al composite sheets: A comprehensive study on deformation behaviors

Compared with monolithic metal sheet, Single Point Incremental Forming (SPIF) of bimetal composite sheet has attracted increasing attention, as it takes advantages of materials with different superior properties, such as high strength, low density, and good corrosion resistance. However, deformation behaviors of bimetal composite sheet in SPIF may differ from the single-layer sheet, which depends on the layer arrangements and mechanical properties of each layer. In this regard, a comprehensive study was conducted to investigate the deformation behaviors of roll-bonded Cu-Al composite sheets in SPIF through predictive modeling, including analytical, empirical as well as numerical approaches, and extensive experimental work taking into consideration effects of key process parameters. It was demonstrated that overall, the formability, surface roughness, thickness variation and forming force in different layer arrangements, in terms of various process parameters, follow the similar trends to single-layer sheets. However, it was further revealed that deformation mode of layer-up sheet tends to a compression state and that of layer-down sheet tends to a stretching state. This leads to higher formability and larger forming force in Al/Cu layer arrangement compared to Cu/Al layer arrangement, as the exterior thinner but stronger Cu layer could endure more stretching deformation.