Effects of annealing on the mechanical and interface properties of stainless steel/aluminum/copper clad-metal sheets

A three ply clad sheet, comprised of austenitic stainless steel (STS304), aluminum (Al1050) and copper (C1220) was fabricated by means of a hot-rolling process at 350 °C and the mechanical and interfacial properties were investigated for use in cook-ware applications. Tension tests on the clad sheet and the individual component metals were carried out at elevated temperatures from 100 to 400 °C. For the clad sample annealed at 400 °C for 30 min, a compound layer was formed at the Cu and Al interface. The thickness of the layer, which was composed of Al2Cu, was found to be about 7 μm. The compound layer of Al2Cu showed a number of micro-cracks indicating a brittle fracture mode, as evidenced by a Vickers indentation test. The value for elongation for the clad sheet at 400 °C was small compared to each of the component metals. The relatively small elongation of the clad sheet at 400 °C can be attributed to the appearance of a thick intermetallic compound layer of Al2Cu at the interface between Cu and Al.