This paper deals with the additive manufacture of magnesium alloy products of the magnesium-aluminum-manganese-zinc system by plasma surfacing with a reverse polarity current. Special attention was paid to the following points: studying the influence of evaporation of alloying elements during plasma additive surfacing on the material quality; studying the influence of surfacing modes (continuous filling and layer-by-layer filling with cooling at different thermal cycles) on the formation of structure and properties of the synthesized material; specifying the influence of the heat treatment on the structure and properties of the deposited metal. A correct selection of plasma surfacing parameters eliminates porosity and cracks in deposited layers. It is established that plasma surfacing provides a relative structural and phase stability of the previous layers under the influence of subsequent thermal cycles during the workpiece manufacture. In general, the dispersion of the structure of the deposited MA5 alloy is significantly higher than that of the cast and heat-treated metal structures produced by conventional technologies. Plasma surfacing with a reverse polarity current provides a deposited metal with high mechanical properties, i.e. a unique 5–9-fold increase in ductility compared to the cast material with an increase in ultimate strength by 7–10%, both with and without heat treatment.

This paper looks at the structure and properties of the high-strength light Al – Mg – Sc alloy 1580 resultant from the application of plasma welding. It was found that by-layer plasma welding with reverse polarity current ensures the absence of internal defects alongside with high strength, ductility and plasticity in the deposited metal. The authors looked at the strengthening effect produced by by-layer forging and successive by-layer plasma welding. The authors established the effect produced by by-layer forging on the structure and properties of metal in plasma welding. The structural difference is shown between the metal of the lower layers (that are closer to the substrate) and that of the upper layers. It was found that the use of bylayer forging in plasma welding reduces the chances of rapid grain growth triggered by repeated heat cycles and results in grain refinement by 1.5–2 times. It was found that by-layer impacts lead to improved phase composition of the aluminium alloy and a more uniform structure, i.e. prevents the predominant localization of the hardening -phase at the layer boundaries and inhibits coagulation of the intermetallic Al3(Sc1 – хZrх) phases. It was established that the ultimate strength of welded layers is comparable to that of cast aluminium alloy being inferior to that of wrought alloy; the plasticity of welded metal exceeds that of castings by 2–3 times and that of annealed and rolled semi-finished products by 1.5 times.The research was conducted under financial support of the RF Ministry of Education and Science, within the framework of the basic part of the State Assignment (project No. 9.9697.2017/8/9), Government of Perm territory (Perm krai), Ministry of Education and Science of Perm territory (Perm krai), as a pat of the Agreement C-26/795 dated 21/12/2017.