Samara Metallurgical Plant JSC, Moscow, Russia

A. M. Drits, Director for Business and Technology Development, Candidate of Technical Science, e-mail: dritsam@gmail.com

Moscow Polytechnic University, Moscow, Russia
V. V. Ovchinnikov, Professor, Head of the Department of Materials Science, Doctor of Technical Science, e-mail: vikov1956@mail.ru
R. B. Reztsov, Postgraduate Student at the Department of Materials Science, e-mail: anikron_91@mail.ru
R. M. Shumeyko, Master’s Student at the Department of Materials Science, e-mail: reginasumejko@gmail.com

This paper describes the results of a study that looked at the mechanical and corrosion properties of joints made in 10 mm thick plates of aluminium alloy 1901T1 by one-sided friction stir welding (FSW) in air and underwater. It is shown that a higher rate of cooling of the stir zone and the heat-affected zone leads to an approximate 1.5–2% increase in the tensile strength of the joint and metal in the stir zone (seam) compared with FSW in air. The strength factor of the joints is 0.85 to 0.86. The average size of grains in the stir zone of the underwater welded 1901T1 alloy plates is 5.33 μm, whereas in the case of FSW in air the average size of grains in the seam is 9.12 μm. During tensile tests, the fracture of the weld joint formed in 1901Т1 alloy by FSW in air and underwater starts in the zone of thermo-mechanical impact and develops through the heat-affected zone. In the case of FSW underwater, the length of the heat-affected zone is approximately 1.7 to 2.5 times less than that observed in the case of FSW in air. The hardness of the stir zone after FSW in air is similar to that of the base metal, whereas under FSW underwater it exceeds that value. Additional ageing, i.e. after FSW, at the temperature of 170 ^oC for 2 hours leads to decreased hardness of all zones of the joint produced by FSW in air and underwater. Both after welding in air and underwater and additional ageing at 170 ^oC for 2 hours, the fracture of the metal in the stir zone obtained as the result of tensile testing is distinctly ductile, with typical pits at the surface. The intercrystalline corrosion of the base metal is 85 μm. During FSW in air, both the heat-affected zone (90 μm) and the stir zone (the seam metal) (96 μm) are equally prone to intercrystalline corrosion. At the same time, during FSW underwater the depth of intercrystalline corrosion is reduced to 27 μm in the seam metal and to 35 μm in the heat-affected zone.
This research was carried out under Project No. 22-19-00121: Regularities of Structural and Phase Transformations in Aluminium-Calcium Alloys Doped with Zinc and Magnesium; the funding was provided under a grant by the Russian Science Foundation.

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