Improvement of mechanical properties of tri-metallic 7075Al/1060Al/304 SS composite via collaborative strengthening behavior

Abstract

In the present work, the mechanical behavior of tri-metallic 7075Al/1060Al/304 stainless steel (Al/Al/Steel) composites was systematically investigated, emphasizing the effect of the strengthening mechanism introduced by interlaminar and internal microstructures of constituent layers. The results show that the excellent interface bonding of tri-metallic Al/Al/Steel composites was achieved by the combined bonding method of roll-casting and rolling bonding, and the intermetallic compounds were effectively inhibited due to the severe deformation caused by the re-bonding process. It is found that an interfacial transition zone (ITZ) appeared at the 1060Al/Steel interface for all specimens after hot rolling bonding, and the increasing thickness of ITZ can be observed with the increasing rolling reduction. The experimental observation indicated that the ITZ was independent of the intermetallic layer, and its formation was mainly due to the plastic deformation introduced by the shear effect during rolling. Compared with the bi-metallic Al/Steel, the mechanical properties of the tri-metallic Al/Al/Steel composites were significantly improved, which was attributed to the contribution of the high-performance 7075Al with precipitation strengthening behavior according to the rule of mixture. Besides, various annealing treatments were conducted to evaluate the effect of mechanical incompatibility on the mechanical properties of tri-metallic Al/Al/Steel composites. The increasing strain gradient led to considerable dislocation pile-up near the interface of the soft 1060Al layer, inducing an extra strengthening mechanism to the tri-metallic Al/Al/Steel composites, which promoted the optimization of strength and ductility.