The influence of Mg addition on phase composition and mechanical properties of twin-roll cast Al-steel clad material

An Al alloy with Mg addition - AA5083 has been used to fabricate an AlMg-steel plate composite via twin-roll casting. Upon annealing at 500-600 degrees C an intermetallic layer forms at the Al-steel interface, comprising of orthorhombic Al5Fe2, monoclinic Al13Fe4 and FCC Al18Cr2Mg3 phases in the order from steel. The complexity of the formed intermetallic compounds (IMC) increases with the annealing time and temperature. The IMC-steel interface remains relatively smooth in all conditions, whereas the IMC-Al interface is unequal and the IMC interlocks with the Al matrix. The complexity of the IMC-Al interface causes breaking of IMC in its interiors rather than at the IMC-Al interface, as was the case with the material without Mg addition. The IMC grows with parabolic kinetics, and the activation energy for the IMC growth was calculated to be Q =148 kJ/mol. During insitu tensile testing using the scanning electron microscope, the IMC layer cracks perpendicular to the interface at regular intervals. The cracks serve as preferential sites for the slip bands initiation. Due to a weaker bonding of the layers, debonding takes place during the deformation, and the Al layer fractures at first.