A cold roll bonding process is applied to fabricate an AA6061/AA5052/AA6061/AA5052 multi-layer sheet. Two AA6061 and two AA5052 sheets with 2mm thickness are stacked alternately to each other, and reduced to a thickness of 2 mm by multi-pass cold rolling. The roll bonded multi-layer sheet is then hardened by natural aging (T4) and artificial aging (T6) treatments. The as roll-bonded sheet shows a typical deformation structure that the grains are elongated to the rolling direction. However, after T4 and T6 aging treatments, it has a recrystallization structure consisting of the coarse equiaxed grains in both AA5052 and AA6061 sheets. The as rolled material shows a lamella structure in which AA5052 and AA6061 sheets are stacked alternately to each other, having higher hardness in AA5052 than in AA6061. However, T4 and T6 aging treated materials show a different lamella structure in which the hardness of the AA6061 layers is higher than that of the AA5052 layers. The strengths of the T4 and T6 age-treated specimens are found to increase by 1.3 and 1.5 times respectively, compared to that of the starting material.

A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA1050 multi-layer sheet. Three Al sheets in which an AA6061 sheet is inserted inside two AA1050 sheets of 2 mm thickness, 40 mm width and 300 mm length were stacked up after surface treatment, and the material was then reduced to a thickness of 1.0 mm by multi-pass cold rolling. The AA1050/AA6061/ AA1050 laminate complex sheet fabricated by roll bonding was then hardened by a natural aging (T4) and an artificial aging (T6) treatments. The microstructures of the as-roll bonded and the age-hardened Al complex sheets were revealed by optical microscope and electron back scatter diffraction analysis, and the mechanical properties were investigated by tensile and hardness testing. The strength of the as-roll bonded complex sheet was found to increase by 2.6 times, compared to that value of the starting material. Both AA1050 and AA6061 showed a typical recrystallization structure in which the grains were equiaxed after heat treatment. However, the grain size was smaller in AA6061 than in AA1050.