The features of the formation of the microstructure of welded joints of sheets of aluminum alloy V-1381 of the Al – Mg – Si – Cu system, obtained with various parameters of automatic argon-arc welding, were studied. Welding modes were selected that provide a high-quality welded joint and strength at a level not lower than 0.8 of the strength of the base metal. It has been established that welding without filler wire leads to cracking without applying tensile deformation, the use of Sv1221 filler wire compared to SvAMg61 and SvAK5 leads to an increase in the strength characteristics of welded joints by 15 – 20 %. Corrosion resistance of welded joints of sheets from V-1381 alloy was determined. Various experimental modes of laser welding were tested, the microstructure and mechanical properties of welded joints were studied. Parameters have been selected that ensure high quality of welds. The possibility of using laser welding for semi-finished products from alloy V-1381 has been established. The new V-1381 alloy can be recommended for use in aircraft fuselage structural elements, including as an alternative to less corrosion-resistant non-weldable alloys of the D16 type, which will increase the weight efficiency of structures both due to increased strength and through the use of welded joints instead of riveted ones.

A new series 6xxx Al-Mg-Si alloy is developed with grade V-1381. The influence of the composition and modes of heat treatment on the mechanical and corrosion properties of sheets with a thickness of 1 and 3 mm manufactured at the All-Russian Scientific Research Institute of Aviation Materials (VIAM) is investigated. The average properties of the sheets are as follows: the ultimate tensile strength is σ B = 410 MPa, the yield strength is σ 0.2 = 360 MPa, the elongation is δ = 11.5%, the fatigue crack growth rate is (dl/dN) = 0.59 mm/kcycle at ΔK = 18.6 MPa m 1/2 , the intergranular corrosion is IGC ≤ 0.15 mm, and the exfoliation corrosion (EXFC) is 4 points. It is found out that the sheets are structurally recrystallized, the main strengthening phase is the matrix-coherent β'(Mg 2 Si) phase evenly distributed with a high density across the volume of grains. Another observed process is the heterogeneous origin of the β′ phase on dislocations and dispersoids. The dispersoids observed in the tested specimens have various morphologies. The grain boundaries have emission-free zones 15-20 nm in width. The temperatures and heat values of phase transformations in ingots and sheets are determined, including the measurement of liquidus and solidus points. The sheet weldability is evaluated by automatic argon-arc welding, and critical strain rate V cr of the weld metal during crystallization is determined at which this metal is not covered with cracks. A laser welding mode has been developed to ensure optimal formation of the geometric parameters of the weld.

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The results of the development of a new alloy of the Al – Mg – Si system of the 6xxx series, which received the V-1381 grade, are presented. The influence of the composition and modes of heat treatment on the mechanical and corrosion properties of sheets with a thickness of 1,0 and 3,0 mm, manufactured under the conditions of FSUE “VIAM”, was investigated. Average level of sheet properties: UTS = 410 MPa, YTS = 360 MPa, El = 11.5 %; fatigue crack growth (dl/dN) = 0,59 mm/kcycle at ΔK = 18,6 MPa·m1/2, intergranular corrosion ≤ 0,15 mm, exfoliation corrosion 4 points. It was found that the structure of the sheets is recrystallized, the main strengthening phase is the coherent matrix β’(Mg2Si)-phase evenly distributed in the volume of grains with a high density. There is also a heterogeneous origin of β′-phase on dislocations and dispersoids. At grain boundaries there are zones free from emissions with a width of 15 – 20 nm. Dispersoids of various morphologies are observed in the tested samples. Temperature and heat values of phase transformations in ingots and sheets are determined and established liquidus and solidus points. The sheet weldability was evaluated by automatic argon-arc welding and the critical rate of deformation of the weld metal during crystallization was determined, at which no cracks were formed in it. Laser welding mode has been developed to ensure optimal formation of geometric parameters of the weld.

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