Abstract: In order to optimize the process of friction stir welding(FSW) and supply the information to the further machine, it is significant to measure the residual stress distribution in the FSW weldment of Al alloy. A domestic invented short wavelength X-ray diffractometer(SWXRD) is employed to determine the internal residual stresses in 2024-T351 Al alloy FSW weldment using both d0 mode and sin2ψ mode. The residual stress distribution results which obtained using SWXRD, neutron diffraction and high energy synchrotron respectively are compared and analyzed. Meanwhile the microstructure in the weldment is observed and the hardness in the center layer of plate is measured. The results show that the internal residual stress in Al alloy FSW can be determined by SWXRD. As for 2024-T351 Al alloy weldment, there are three tensile stress peaks, two tensile peaks located in the heat affected zone(HAZ) and another on the weld line. The result of d0 mode is identical with results of other methods such as neutron diffraction and synchrotron diffraction. The stress distribute in the weld nugget zone(WNZ) of the FSW weldment determined using sin2ψ mode fit well with the result of d0 mode. However the sin2ψ mode can not used to measure the stress distribution in the other zone such as thermal-mechanically affected zone(TMAZ), HAZ and base material zone(BMZ) due to strong texture. It is an applicable method to determine internal residual stresses combined sin2ψ and d0 mode together by SWXRD.

Key words: Aluminum alloys, Friction stir welding, Internal, Residual stresses, Short wavelength, X-ray diffraction