Effects of Initial Microstructure on Mechanical Properties of AA1050/AA2024 Laminated Metal Composite Fabricated by Accumulative Roll Bonding Process

In this study, effects of initial microstructures on tensile properties and bending performances of AA2024/AA1050 laminated metal composite (LMC) produced by accumulative roll bonding (ARB) process at elevated temperature were investigated. The AA2024 alloy was primarily subjected to T3 and annealing treatments. Instead of Al₂Cu phase in the annealed alloy, the T3 aged alloy contained Al₂CuMg precipitate, which effectively impeded grain growth during the ARB. Moreover, two initial conditions of the AA1050 alloy were considered, namely, annealing prior to cold-rolling and reverse step, resulting in elongated and recrystallized structures, respectively. The precipitates in the AA2024-T3 alloy provided layers with finer grains and greatly increased high angle grain boundaries, leading to laminates having the highest yield and tensile strength which were 56% and 20% larger than those composed of the annealed alloys, respectively. On the other hand, elongations and toughness of LMCS produced by ultimately annealed AA1050 alloy were 3.6 and 2.5 times higher than those consisted of the aged and rolled alloys, accordingly, due to lower layer waviness and reduced strength incompatibility between constituent layers. In bending test, the achievable stresses of LMCs were governed by stronger layers, while stress decline state and resulted bending toughness were attributed to crack onset at the bottom layer. Combining with the softer annealed AA2024-T3 alloy caused more uniform stress transfer, strain distribution and thus delayed crack initiation, whereas bending strength of LMCs could be increased up to 96% when using the aged and rolled alloy sheets.

Graphical Abstract