Roll-Bonded Tri-Layered Mg/Al/Stainless Steel Clad Composites and their Deformation and Fracture Behavior

The deformation and fracture behaviors of roll-bonded tri-layered Mg/Al/stainless steel (SST) composite plates were studied. Brittle interfacial reaction compounds were observed at the Mg/Al interface upon annealing at and above 573 K (300 A degrees C), whereas no visible interfacial reaction compounds were observed at Al/SST interfaces even after annealing up to 673 K (400 A degrees C). The strength of the tri-layered Mg/Al/SST clad plates is in close agreement with those calculated from the strength data of the separated Mg, Al, and ST layers using the rule of mixture. The fracture strain components of the tri-layered clad in the absence of brittle interfacial intermetallic layer far exceed those calculated based on the fracture strain data of separated Mg, Al, and SST sheets. The enhanced ductility of the clad composites is due to the suppression of the localized deformation in a metallic layer by other metallic layers caused by the mutual constraint imposed by an adjacent layer. On the other hand, the fracture strain was found to be reduced in the presence of intermetallic layers between the metallic substrates. Cracks perpendicular to the stress axis were observed in the intermetallic compound layer between Mg and Al, inducing the localized slip in the vicinity of intermetallic cracks and premature fracture of the Mg alloy layer.