Mechanical Properties And EBSD Analysis Of Friction Stir Welded Joint For 2024-T4/7050-T7451

The Friction Stir Welding (FSW) of 2024-T4/7050-T7451 aluminum alloys has been done at the given welding parameters based on the studies of FSW technology, parameters choosing and research situations in this thesis. The microstructures, micro-hardness, residual stress and EBSD analysis of the FSW joints have been investigated. The mechanical properties of the FSW joints have also been gotten by tensile testing, and the fracture mechanisms have been studied by fracture surface analysis.The research results indicate that good mechanical properties of FSW joints have been got at the given welding parameters. The tensile strength of untreated FSW joint of 2024-T4/7050-T7451 aluminum alloys is 70.1% of that of 2024-T4 aluminum alloy, and is 60.5% of that of 7050-T7451 aluminum alloy. The tensile strength of treated FSW joint is 55.9% of that of 2024-T4 aluminum alloy, and is 47.7% of that of 7050-T7451 aluminum alloy. Uniform and fine microstructures have been found at the welded nuclear area of the FSW joints. The distribution of micro-hardness appears‘W’model, and the maximum value of micro-hardness is generally at the nugget zone of the FSW joints, while the distribution of residual stress appears‘M’type. The fractures of the FSW joint are ductile, and the fracture occurs at the region between TMAZ and HAZ in the retreating side of joints. EBSD analysis show that orientation distribution of grains in the nugget zone is irregular, and the misorientations of grain boundaries are large, while orientation distribution of grains in the base material is still as rolled condition, and the misorientations of grain boundaries are small.The research results of this paper give ideal welding parameters for FSW of 2024-T4/7050-T7451 aluminum alloys. At the same time, the data of mechanical properties are important for the structural design of the FSW components.