| Friction Stir Welding (FSW) is a solid state welding method developed by TWI in the 1990s,and as well as an important new welding technique with potentially significant application in automotive and aerospace industry. In this welding process, a rotating welding tool is driven into the material at the interface of, for example, two adjoining plates, and then translated along the interface.The object of this research was to investigate the characteristics of joining, microstructures and mechanical properties of FSW joints welded for experimental aluminum alloys, such as LY12, L2, and LF2 with different thickness and the influence of welding parameters including most importantly the tool's rotational speed, welding velocity, and welding energy on the quality of joint according to the solid-state joining principle during FSW welding. Finally, the optimal welding parameters for different materials under experimental condition were completed on the basis of correlative studies. Furthermore, roles of the influences of welding parameters on welding joints were established: (1) influence of rotational speed on joint: strength of joint will increase firstly, then decrease; the average value of hardness in weld nugget could fall; microstructure could be fine and then bigger with the increase of rotational speed.(2) influence of welding velocity: strength of joint will decrease while the value of hardness in weld nugget and microstructural dimension will enhance with the increase of welding velocity.(3)influence of welding energy: variation of joint strength was in accordance with the role of with rotational speed whereas the value of hardness in weld nugget and microstructural dimension are contrary to the result above.The results of investigations not only provide data for FSW welding experiment, but also can support the further study of techniques of FSW method. |
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