ARKONIK SMZ JSC, Moscow, Russia:

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

Moscow Polytechnic University, Moscow, Russia:
V. V. Ovchinnikov, Head of the Department of Materials Science, Doctor of Technical Sciences, Professor

NPO Mashinostroeniya Military & Industrial Corporation, Reutov, Russia:
I. V. Solovieva, Head of the Metallography and Mechanical Testing Laboratory

SESPEL Cheboksary Enterprise CJSC, Cheboksary, Russia:
V. A. Bakshaev, Director

This paper describes the results of a study that looked at mechanical and corrosion performance of joints between 3 mm thick 1565ChН116 aluminium alloy sheets produced by friction stir welding in atmosphere and in water. It was established that a higher in-water cooling rate resulted in a higher tensile strength of the weld joint and slightly impacted its properties. It is the thermomechanical impact zone of the joint that sees fracture during tensile testing when aluminium alloy 1565ChН116 is friction stir welded in atmosphere and in water. The strength of such joint is 95 to 99% of the strength of the base metal. When conducting friction stir welding in water, the thermal impact zone is approximately 1.6 to 2.2 times shorter than when the process takes place in atmosphere. For the alloy 1565ChН116, friction stir welding conducted in water is associated with a 10 to 12% higher microhardness of metal in the thermomechanical impact zone and the stirring zone. The grain size in the stirring zone was observed to decrease from 6.8 to 4.5 μm. In this zone (the core of the joint), small angle boundaries account for approximately 15% of the total number of boundaries. This suggests that the structure mainly consists of equiaxed grains with large angle boundaries. A transmission electron microscopy study of foil obtained in the joint core area confirmed the results of phase and microtexture analysis (carried out by means of the EBSD technique) indicating that a recrystallized structure formed in the centre of the joint. A higher cooling rate during friction stir welding increases the intercrystalline corrosion resistance of all areas of the joint by approximately 1.4 to 1.7 times. The biggest increase in the intercrystalline corrosion resistance was observed in the thermal impact zone.

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