The Paton Welding Journal, 2016, #5-6, 86-90 pages
Features and advantages of the process of friction stir welding of butt joints of sheet aluminium-lithium alloys
A.G. Poklyatsky, V.V. Knysh, I.N. Klochkov And S.I. Motrunich
E.O. Paton Electric Welding Institute, NASU
11 Kazimir Malevich Str., 03680, Kiev, Ukraine. E-mail: firstname.lastname@example.org
The paper analyzes the structural features, strength and fatigue life properties of sheet joints of Al–Li alloys 1420 and 1460, produced by nonconsumable-electrode argon-arc welding and friction stir welding. It is shown that application of FSW provides formation of permanent joints with minimum level of stress concentration in the points of weld transition to base material and allows avoiding defects in welds in the form of pores, oxide film macroinclusions or hot cracks due to melting and solidification of metal in fusion welding. Here, intensive plastic deformation of metal under the tool shoulder and in weld nugget results in formation of fine-crystalline (3–4 µm) uniform disoriented structure, and grain elongation and distortion in the direction of plasticized metal displacement proceed in adjacent sections. This leads to increase of hardness and ultimate strength of joint weld metal. Lowering of the temperature of heating of the edges being welded provides reduction of maximum level of tensile residual longitudinal stresses in welded joints, compared to TIG welding. It is found that fatigue resistance characteristics of butt welded joints, made by FSW, are superior to those of the joints, made by TIG welding. 10 Ref., 9 Figures.
Al–Li alloys, friction stir welding, defects, microstructure, ultimate strength, fatigue resistance
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