The aim of this study is to develop a gradient structure in AA1050 aluminum sheet using roll bonding and annealing. For this purpose, the 3-layered aluminum samples with lateral layers being reduced in initial thickness by 20, 35, and 50 percent to achieve smaller grain size in surface and an unrolled middle layer, were roll bonded at ambient temperature and without lubrication. afterwards, in order to obtain appropriate flexibility and toughness, the samples were annealed at a temperature of 380 ºC for 15 to 2800 seconds. Subsequently, the microstructural evolutions and mechanical properties were investigated. The changes in microstructure after roll bonding and annealing were studied through optical microscopy. The distinction of grain size in the lateral layers and the central layer was evident. The grains grew larger as the annealing time increased and the maximum was achieved at 600 seconds. Thereafter, the growth rate decreased drastically. Also, by extending the annealing duration, the structural gradient between the central layer and the lateral layers decreased, meaning that the average grain size in layers became closer in value. Uniaxial tension, shear punch and bending tests were utilized to eva‎luate the mechanical properties and failure behavior. An increase in toughness was visible in most of the samples. The results of the tensile tests propose that the samples with an annealing time of 120 seconds demonstrate a significant improvement in strength, as well as flexibility, and the sample with a 20% reduction in initial thickness and annealing time of 120 seconds in 380 ºC presented the best toughness with 46.39 MJ/m. The bending test also showed that the bending resistance increased with the annealing time. The fracture cross section was eva‎luated by scanning electron microscopy and it was observed that the width and depth of the dimples in the central layer is greater compared to in the lateral layers, which can be attributed to the initial grain size in these layers. As a result, the central layer experienced a more ductile fracture than the lateral layers.

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