Effect of heat treatment on formability of AA6061 aluminum alloy in the sheet hydroforming process

Today, the use of aluminum alloy metal sheets in the shipbuilding industry is expanded due to its high strength to weight ratio and good corrosion resistance. Due to the low formability of this alloy at room temperature, the deep hydrodynamic drawing process of AA6061 aluminum alloy double-stepped part under different heat treatment cycles has been experimentally investigated in this study. Firstly, the maximum forming depth before sheet rupture was obtained at different oil chamber pressures under the initial T6 heat treatment and 12bar was selected as the best sheet forming pressure. The results show that although by choosing the appropriate process parameters, these sheets can be formed with the least defects such as cracking and wrinkling, but the formability depth is very limited in the initial T6 state. Therefore, the effect of solution, aging and annealing heat treatments on the depth of forming, hardness and thickness distribution of hydroformed parts was investigated. Solution heat treatment at the sutiable temperature and time can improve the formability of the parts in the hydroforming process by 91.7%, while the hardness of the part is reduced by 36.2% compared to the initial T6 state. Hydroforming after the aging process reduces the formability by 16.7%, due to the increase in part hardness by 11.9% compared to the initial T6 state. With annealing heat treatment, the forming depth is improved by 116.7% compared to the initial T6, which results in a 69% reduction in the hardness of the workpiece.