| The General Armament Department of PLA has invented a new type aluminum copper alloy(an interim name of the 2519)thick plate aluminum alloys during the 10th Five-Year Plan and the 11th Five-Year Plan. 2519 is used in the airplane outer covering, the rockets, the ships and the amphibious armored assault vehicle. While the craft of welding the 2519 aluminum alloy is not mature, especially the method of friction stir corner welding. The craft of friction stir corner welding is one of the key techniques that we must conquer. In this paper, we bring forward a new method of friction stir outer corner welding and research the basal outer corner welding mechanism and the key technique applying FSW.We based on computational fluid dynamics theory and used commercial software Fluent to establish flow and temperature model of friction stir outer corner welding, found the rule about the temperature and the flows. When modeling, a whirly conical concave replace the effect of the shoulder. According to the actual situation, we use two angle axis to simulate the obliquity of stir pin spool and the work piece the vertical direction, which lead to lower temperature in front of stir pin than in back. Adding the contact thermal resistance to the model, and the rule about the temperature changes its form from a similarity shape of tundish to chuckhole. We analyzing that excessive contact thermal resistance will bring on degrading fluid and result in disfigurement. Comparing the flows different formed by the two kind of stir pins which has its different spiral angle. Using the simulation result, we have welded the high-strength 2519 aluminum alloy, which proves this method is feasible, and analyses the disfigurement through analysis the mechanical properties of the microstructure and hardness distribution of the welding line. We can draw the conclusion that weld nugget zone (WNZ) is the lowest zone about the mechanical capability. |
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