Investigations on Formability of a SS/AA Clad Sheet at Elevated Temperatures

The present study investigated the various aspects of mechanical behaviour, microstructure evolution, and formability of a SS430/AA1050 clad sheet at three different elevated temperatures with or without lubrication. Tensile experiments revealed a reduction in tensile strength and ductility of the SS430 layer at elevated temperatures, while the AA1050 layer showed a decrease in strength but an increase in its ductility when compared to that of at room temperature. The average normal anisotropy was also increased for both layers of the sheet, enhancing overall clad sheet formability. At elevated temperatures, recovery and recrystallization influenced texture intensity significantly, especially in AA1050, resulting in a more random distribution of grain orientation, however, the texture of SS430 become stronger after deformation. With MoS2 as lubrication, friction values decreased notably for both the layers, reducing sticking friction during forming operations. Forming limit diagrams demonstrated improved limit strains under lubrication, with major strain at plane strain condition increasing more than 65% at 300°C compared to the dry conditions. Deep drawing experiments of the clad sheet revealed that the lubricant significantly improved drawability at all temperatures. Also, the use of lubrication increased the limiting draw ratio, with a maximum draw ratio of 2.0 achieved at 300°C. An analytical model was also developed to predict the required punch force in the deep drawing of the clad sheet based on the Barlat-89 anisotropic yield criterion. The results achieved by numerically and analytically were observed to be in a good agreement with the experimental results.