Abstract
The aim of this research was to investigate the effect of different heat treatment conditions of AA2519 friction stir welded joints on their microstructure and residual stresses. The following welding parameters have been used: 500 rpm tool rotation speed, 150 mm/min tool traverse speed, tool tilt angle 2°, pressure force 17 kN. The welded material was investigated in three different configurations: HT0, HT1, and HT2. The first type of weld (HT-0) was made using AA2519 alloy in non-precipitation hardened state and examined in such condition. The second type of weld (HT-1) has been performed on AA2519-T62, that corresponds to precipitation hardening condition. The last type of weld (HT2) was performed on annealed AA2519 and the obtained welds were subjected to the post-weld precipitation hardening process. The heat treatment was carried out in two stages: solution heat treatment (530 °C/2 h + cooling in cold water) and aging (165 °C/1 0 h). Residual stresses were measured using X-Ray diffraction patterns obtained from Bruker D8 Discover X-ray diffractometer utilizing the concepts of Euler cradle and polycapillary primary beam optics. The conducted research indicates that the best material properties: homogenous microstructure and uniform distribution of microhardness and compressive state of residual stresses were obtained for the HT-2 series samples subjected to heat treatment after the friction stir welding (FSW) process.
Highlights
The reduction of energy consumption, especially in the automotive and aerospace industry is one of the greatest challenges facing modern civilization
The image microstructure of AA2519 is presented in Figure to the rolling direction and it consists of
The microstructure of AA2519 aluminum alloy is characterized by elongated grains oriented parallel to the rolling direction and it consists of Al matrix and Al2Cu precipitates
Summary
The reduction of energy consumption, especially in the automotive and aerospace industry is one of the greatest challenges facing modern civilization. This task can be accomplished by replacing the previously used materials with their lighter counterparts and introducing new technologies in the production process [1,2]. The friction stir welding (FSW) method is meeting these difficulties. In this technique, the rotating tool is inserted into the contact zone of the pressed elements to such a depth that there is friction between the shoulder and the surface of the joining elements [8]. A weld is obtained, within which the Materials 2020, 13, 834; doi:10.3390/ma13040834 www.mdpi.com/journal/materials
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