Friction stir welding characteristics of two aluminum alloys

The friction stir welding characteristics of the strain hardened AA1050 H24 and precipitate hardened AA2017 T351 aluminum alloys were examined in order to reveal the effects of the alloy properties on the friction stir welding behavior of the base materials. The results show that (1) for AA1050 H24, the weld possesses a smooth surface and clear ripples, there is no elliptical weld nugget in the weld, there is not discernible interface between the stir zone and the thermo mechanically affected zone(TMAZ), and the internal defect of the weld looks like a long crack and is located in the lower part of the weld; (2) for AA2017 T351, the weld usually possesses a rough surface and visible ripples, the elliptical weld nugget clearly exists in the weld and there is obvious plastic flow and a discernible interface between the nugget and the TMAZ, and the internal defect of the weld is composed of many voids and distributed in the middle part of the weld; (3) the effective ranges of the welding parameters for AA1050 H24 and AA2017 T351 are both narrow, especially for the latter; and (4) the tensile strength efficiencies of the joints for the two typical alloys are similar, i e 79% for AA1050 H24 and 82% for AA2017 T351.