Architectured lightweight steel composite: evaluation of the effect of geometrical parameters and annealing treatments on deformation behavior

Architectured lightweight steel composites were designed and fabricated through the cold roll bonding (CRB) of stacked steel-aluminum sheet layers. The effects of geometrical parameters including thickness ratio (TR) and the number of constituent layers on bond strength and tensile properties of the composites were evaluated using peeling and tensile tests. It was found that by decreasing the TR of aluminum to steel from 0.5 to 0.2, the bond strength increased in the as-rolled specimen. However, it led to a decrease in the bond strength of the annealed sample by the facilitation of the formation of Fe–Al intermetallics along the interfaces. In order to obtain a more in-depth understanding of deformation behavior at the interface of steel/aluminum layers, strain gradient at these regions was evaluated through the measurement of dislocation density using the XRD analysis. Macrotexture measurement and anisotropy analysis were also carried out to evaluate the formability of the optimized sample. Moreover, it was found that by increasing the number of layers, the bond strength decreased due to the insufficient extrusion of the virgin metals to the interface of the layers. Higher steel/aluminum interfaces as effective microstructural heterogeneities improved the elongation in five-layered and seven-layered composites by arresting the propagating cracks. Employing the concept of laminated composite led to the production of a lightweight architectured steel with density of 5.6 g.cm−3, which can be a promising structural material for automotive applications.