Investigation on the bond strength of Al-1100/St-12 roll bonded sheets, optimization and characterization

Al-1100/St-12 aluminum clad steel sheets were produced using roll bonding process at different reductions in thickness and with various supplemental annealing treatments. Experiments were conducted by applying the Taguchi method to obtain optimum condition for maximizing the joint strength. The joint strengths of the bi-layer sheets were evaluated by peel test. The Al/Fe intermetallic phases at the joint interface and the peeled surfaces were examined using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) and Vickers microhardness test were performed to characterize the intermetallic compounds. The results indicate that at the optimum condition of 0.50 reduction in thickness, 450 °C annealing temperature and 90 min annealing time, the bond strength reaches to the base aluminum sheet strength. In comparison to the reduction in thickness and annealing time, the annealing temperature has the most influence on the joint strength changes. In general, raising the annealing temperature up to 450 °C, increases the joint strength. However, annealing treatment at 500 °C reduces the strength due to the formation of brittle Al/Fe intermetallic layer at the bond interface. Additionally, increasing the reduction in thickness improves the joint strength.

► Taguchi method was used as a statistical procedure to find the optimum condition.
► Analysis of variance was considered to determine the contribution of each factor.
► Correlation between the joint strength and intermetallic phase formation was studied.
► Enhancement of annealing temperature up to 450 °C, increases the joint strength.
► Annealing time effect on the joint strength is dependent on the temperature.