Abstract: The welding experiments of fillet welded joints with 150-degree are performed for 2A14-T4 aluminum alloy thick plate by using the self-developed stationary shoulder friction stir welding(SSFSW) tools with the pin of 8.5mm length, and the influences of welding parameters on the microstructures and mechanical properties of fillet welded joints are explored and discussed. It is shown that the defect-free fillet welded joints with smooth weld surface can be produced in the range of 500-700 r/min rotational speeds and 40 mm/min-100 mm/min welding travel speeds, the shape and size of fillet joints can be controlled accurately and almost no any residual welding angular deformation is produced. The weld zone is mainly composed of stir zone(SZ), the shape of SZ is similar to the cone of stirring pin or elliptical shape, and its width is evenly distributed across the thickness of the plate; the widths of the thermal-mechanical affected zone(TMAZ) and heat affected zone(HAZ) are obviously smaller. The microhardness distribution is apparently uneven in the weld zone, and the weakest site is located at the interface between TMAZ and HAZ. The rotational speed has little effect on the average microhardness of the weld zone, but with the increase of welding speed, the average hardness increases obviously. The equivalent tensile strength(ETS) of the advancing side(AS) of the fillet welded joint is higher than that of the retreating side(RS). The ETS decreases with the increase of rotational speed but increases with the increase of welding speed. The ETS obtained at the welding process of 500 r/min-100 mm/min has the highest value, reaching 79.24% of the base material. The tensile specimens in the tension-shear loading modes have minor macro-plastic deformation and present the feature of the brittle fracture process.

Key words: 2A14 aluminum alloy, fillet welded joint, stationary stir friction stir welding, microstructure features, mechanical properties