| 2024 aluminum alloy belongs to the heat-treatable aluminum alloys and has been widely used in aircraft skin sheet, wing beam and many other different fields. Moreover, its application field is still expanding with the development of high and new technology. However, the special weldability of aluminium alloys makes these alloys susceptible to hot cracks, gas porosity and some other defects. In addition, the strength coefficient of its welded joint is usually lower than that of the base metal, which limits its application to certain extent. In order to obtain welded joint with excellent properties, welding procedure and parameters should be established appropriately according to the structure and demension. In this paper, 2024 aluminium alloys with defferent thickness are welded by TIG, MIG and EB welding respectively. The mechanical properties and microstructures of welded joints are investigated sysmetically, and welded joints with good quality are obtained by optimized welding parameters. Finally, the welding temperature field under MIG and EB welding procedure are analysed based on double-ellipsoid heat source model by means of ANSYS software. The loading and unloading processes of the moving thermal source are implemented through the APDL computer language, and the temperature filed distribution of different welding process is analyzed. All these computation results will provide theoretical guidance for welding parameters optimimum.Results show that the tensile strength of all three different welded joints is lower than that of the base metal, and the EB welded joint has the highest strength, MIG the meduim, TIG the lowest. In general, the tensile strength of MIG and EB welded joint can meet the mechanical properties reqirements in practical engineering structure. Micrographs of the three different welded joints indicate that the weldment microstructure of EBW joint is composed of fine equiaxed grains and even-distributed eutectic structure. However, the weldment microstructure of TIG and MIG welded joints shows equiaxed dendritic apperance, and the grain size is obviously lager than that of EB joint. Although the HAZ microstrcture of all the three different joints is composed of coarse column dendritic, the grain size of EW welded joint is obviously smaller than the other two types. The fractographs of joint tensile specimens are observed by SEM, and the results indicate that the fracture surface of TIG welded joint appears to be a river pattern which it presents the typical feature of cleavage fracture. However, many dimples can be seen in the fracture surface of MIG and EB welded joint and many small particles distribute at the bottom of the dimples, which show evident dimple rupture. Phase constituent of three different welded joints are conducted with X-ray diffraction (XRD). Results show that the three types of welded joints mainly containα-Al matrix. In addition, it is also found that there is onlyθ(CuAl2) strengthening phase and Si-phase in TIG welded joint,θ(CuAl2) and Mg2Si as the strengthening phases in MIG joint, whileθ(CuAl2) and S (Al2CuMg) are acted as main strengthening phases in EBW joint. And further analysis by transmission electron microscopy (TEM) confirmed thatθ(CuAl2) is the main strengthening phase in the joints.The welding temperature fields of 2024 aluminium alloy plate with 8mm thickness under MIG and EBW welding processes are simulated and analyzed by ANSYS software. Results show that the welding temperature fields obtained by the double-ellipsoid heat source model is more in accordance with actual situation, which verify the reliability of the established heat source model. The results of simulation analysis indicate that the appearance of molten pool is basically consistent with that of practical case. Moreover, the influence of welding parameters on temperature fields are also analyzed, and the results show that the lower welding speed is, the higher the peak temperature of the same point in high temperature region is; the higher the welding power is, the higher the peak temperature of the same point is.The experiment and simulation results indicate that the 2024 aluminium alloy with moderate thickness can be successfully welded by MIG and EB welding under such experiment conditions.
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