| Summary: | 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.
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