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The paper presents the results of research on the development of parameters for obtaining weld joints from aluminum alloys 2024 and 5056 in friction stir welding. The results of the conducted work show a rather complex character of dependence of parameters for obtaining weld joints with tensile strength not less than 0.9 on the tensile strength of the base metal. In general, for all the investigated thicknesses of sheet rolled products, it is characteristic to use lower linear welding speeds and high tool rotation speeds. The clamping force of the tool to the material of alloy 2024 workpieces is slightly higher than when welding alloy 5056 samples. The welding of alloy 5056 specimens is characterized by an insignificant increase in the clamping force in the transition from welding specimens 5 and 10 mm thick, which is not typical for alloy 2024. [ABSTRACT FROM AUTHOR]

The samples produced by friction stir welding of 35 mm thick rolled sheets of thermally non-heat-treatable aluminum-magnesium alloy AA5056 were investigated in this work. Macro- and microstructure was studied on metallographic specimens cut in a planar section relative to the welding zone through the thickness of the workpiece. It was found that in the zone of tool inlet the weld metal is extruded, then there is an adhesive interaction of the tool and welded material with its further layer-by-layer transfer, as a result of which the structure is represented by a mixture of material flows along the contour of the tool. [ABSTRACT FROM AUTHOR]

In the present work, the FSW-joint of 35 mm thick aluminum-magnesium alloy AA5056 sheets was investigated. It was observed that the microstructure is represented by a system of separate metal flows along the contour of the tool. This is caused by lower values of pressure in the area of joint formation relative to the material volume in comparison with welding products of smaller thicknesses. The results of microhardness measurements of the weld material and the near-weld area of fixed joints show that in the material of the main structural zones, there is no softening as compared to the base metal. Tensile tests conducted show high mechanical properties of the samples. The average ultimate tensile strength value is about 305 MPa. Deformation of specimens occurs with pronounced discontinuous fluidity or Portevin– Le Chatelier effect. [ABSTRACT FROM AUTHOR]

The paper is devoted to the study of friction stir welded samples, in which the special high-speed steel tool has been broken during the process of their production. The thickness of the samples is equal to 35 mm. It has been observed that after the tool breakage, the pin section separated from the tool remains in the weld. Around the pin, there is the structure modified by the severe thermomechanical action, which made it possible to estimate the size of the material fragmentation zone in the area ahead of the tool. After the breakage, the tool fragment itself has been deformed by the remaining part of the tool, including the shoulders. It resulted in the layering of the upper part of the pin fragment and the crack propagation into the central part of the pin. Based on the data obtained, it was considered that the tool breakage was caused by the excessive axial force, which resulted in the high tangent loads in the area below the shoulders. [ABSTRACT FROM AUTHOR]

The work compares the strength characteristics and microstructure of 2-mm-thick welded joints from Al-Mg alloy AA5056, produced by friction stir welding along and across the workpiece rolling direction. The tests show that the variation of parameters results in the formation of a complex structure, which is determined by the contribution of both mechanical and thermal components. Depending on the rolling direction, the welded joint has different mechanical properties under identical conditions. In the case of the rolling direction coinciding with the friction stir welding direction, the strongest welded joint has the ultimate tensile strength of 328 MPa, which is equal to 98% of the base metal strength. In case of welding in the transverse direction, the ultimate tensile strength of the joint exceeds those of the base metal by 8 MPa and is equal to 333 MPa. According to the conducted experiments it was proved that the structure and strength of friction stir welded joints depends on the workpiece rolling direction, which implies different welding parameters for these cases. [ABSTRACT FROM AUTHOR]

In this work the study of the friction stir welding process of 2 mm thick aluminum alloy AA2024 sheets cut along and across the rolling direction was carried out. The obtained results show that the rolling direction of AA2024 sheet workpieces has a significant effect on the selection of optimal welding modes. It is revealed that at welding across the rolling direction it is possible to achieve the highest values of the ultimate tensile strength in a rather wide range of modes. [ABSTRACT FROM AUTHOR]

In this paper, regularities of the friction stir welding process parameters influence on mechanical properties of welded joints of different thicknesses are investigated. Joints were produced using the same type of tools with a screw-shaped pin. The tests show different dependencies of the joint mechanical behavior on the welding parameters. 2-mm-thick samples are characterized by high values of the ultimate tensile strength and a small variation of those when changing parameters. 10-mm-thick samples are characterized by a lower ultimate tensile strength and a greater variation at changing process parameters. [ABSTRACT FROM AUTHOR]