Influence of Process Temperature on Hardness of Friction Stir Welded High Strength Aluminum Alloys for Aerospace Applications

The increasing application of innovative materials, such as high strength aluminum alloys, is challenging the manufacturing processes of the Aerospace and Aeronautics Industries. Despite this challenge the processes need to comply with high requirements regarding the reproducibility and the quality of the products. For this reason the adaption of conventional welding technologies to the new materials is considered to be difficult. Therefore, innovative welding technologies such as Friction Stir Welding (FSW) have been developed [1].This paper deals with the implementation of FSW into a new production process for lightweight dome structures of fuel tanks: Starting at temper condition O two AA 2219 plates are joined using FSW technology to form a larger blank. After that, the blanks are formed to shape using spinforming technology. The manufacturing process is accompanied by several steps of heat treatment to accomplish a finished tank-dome in temper condition T8.The studies presented in this paper aimed on finding a correlation between the process parameters and the properties of the welding seam, which are essential for the following spinforming process. For this purpose the experiments were conducted using design of experiments (DoE). The resulting hardness increase of the welding seam was chosen as target variable. Based on the acquired data a regression model was established and used to estimate optimal parameters for dome production.