Samara Metallurgical Plant JSC, Samara, Russia.

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

Moscow Polytechnic University, Moscow, Russia
V. V. Ovchinnikov, Head of the Department of Metal Science, Doctor of Technical Sciences, Professor, e-mail: vikov1956@mail.ru

Moscow Polytechnic University, Moscow, Russia¹ ; GOSMKB Vympel JSC, Moscow, Russia²
D. A. Polyakov, Head of the Process Department², Postgraduate Student at the Department of Materials Science¹, e-mail: da_polyakov@mail.ru

This paper describes the results of mechanical tests conducted for welded joints made in 15 mm 1565chM alloy plates. The welds were made by manual multipass argon-arc welding and by friction stir welding. Scandium-doped SvAMg61 and Sv1575 wires were used as fillers in the multi-pass argon-arc welding process.The paper shows that in the case of FSW of 1565chM alloy plates quality welds can be obtained by using double-sided welding – i.e. by welding alternately on the face and root sides of the joint. During tests, failure of the welded joints made in samples of 1565chM alloy plates by manual multi-pass argon-arc welding and by FSW occurred in the heat-affected zone. The strength factor of the manual argon-arc welded joints was 0.96, while the one of the FSW joints was 0.98. The introduction of scandium in the weld by means of Sv1575 filler wire helps raise the ultimate strength of the joint metal by 23 to 25% compared with SvAMg61 wire. At the same time, the bend angle increased by 45 % and the impact strength – by 20%. It is demonstrated that the FSW joint has higher absolute impact strength values than the base metal, whereas in the case of fusion welding these values are lower in the joint than in the base metal. In the manual multi-pass argon-arc welding of 1565chM alloy plates with Sv1575 filler wire, a fine-grained structure with a eutectic phase precipitated along the grain boundaries can be observed in the joint metal. The grain size is decreased down to 10 to 30 μm, while it is 50 to 100 μm with the SvAMg61 filler wire being used. The highest strength and plasticity were observed in FSW joints made in 1565chM alloy plates. Thus, the ultimate strength of the joint metal was 390 MPa, with the bend angle being 170 degrees and the impact strength being 66 J/cm². In FSW, finer grains of 5 to 6 μm were mainly observed in the stir zone, while the thermomechanically affected zone also contained a small amount of coarser grains with the size of up to 15 to 20 μm. An equiaxial recrystallized structure with 50 to 60 μm grains is typical of the heat-affected zone. One can note the presence of the characteristic onion-shaped structure in the joint metal. A closer examination revealed a double-layer structure of rings: rings of the second layer are observed between the first layer rings. The former can be described as a substructure.
Support for this research was provided under Grant No. 22-19-00121 by the Russian Science Foundation, https://rscf.ru/project/22-19-00121/.

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