Multiscale interfacial structure strengthening effect in Al alloy laminated metal composites fabricated by accumulative roll bonding

This study presents a method to obtain aluminum alloy laminated composites with high yield strength and good ductility through a multiscale coarse/ultrafine-grained design, which are fabricated by accumulative roll bonding (ARB) and subsequent annealing treatment. Experimental results showed that an outstanding combination of strength and ductility was achieved in 1100/7075 Al alloy laminated composites after annealing at 300 °C for 60 min. Deviation between experimental and predicted results from stress-strain curves indicated that an extra strengthening effect was present in the laminated metal composites. Moreover, to analyze the effect of the magnitude of mechanical incompatibility on the mechanical properties during deformation, laminated metal composites with constituent layers possessing different flow properties were comparatively studied. Laminated metal composites with multiscale grain size distributions were obtained using different rolling strain paths and annealing treatments, which was attributed to differences in the recrystallization of constituent metals. It was determined that cross rolling, compared with direct rolling, gave rise to more effective improvements in the mechanical properties after annealing treatments due to higher mechanical incompatibility across the interface. For the Al alloy laminated composites, the difference in flow properties between the constituent layers plays an important role in additional interfacial strengthening by appropriate collocation of component strengths. During tensile deformation, a high density of geometrically necessary dislocations (GNDs) was distributed in the interface of the soft layer due to the mechanical incompatibility across the interface. The high yield strength with a multiscale interfacial structure is attributed to the back stress strengthening associated with the formation of GNDs and the good ductility results from the high strain hardening rate during plastic deformation.