OBRABOTKAMETALLOV technology Vol. 24 No. 4 2022 Fig. 6. Macro- and microstructure of typical specimen of titanium alloy with a thickness of 5 mm after plasma cutting: a – macrostructure; b, c – enlarged images of the upper and lower parts of cut zone; d, e, f – microstructure of specific zones; g, h – microhardness variation; 1 – base metal; 2 – heat-affected zone; 3 – melting zone; 4 – zone boundary; 5 – macrogeometry failure; 6, 7 – areas of microhardness testing or discontinuities occurs. These regions should be removed during further machining of the material. The organization of the structure within the typical structural zones of the specimens is similar to that observed when cutting specimens with a thickness of 5 mm. Microhardness measurements (Fig. 7, e–i) also show that in the boundary area there is a drastic increase in the microhardness of the material compared to the base metal. The research shows a fairly high degree of applicability of all three modes of plasma cutting of specimens with a total thickness of 10 mm, similarly to the cutting of specimens with a thickness of 5 mm. Mode No. 1 is the most optimal, since it is characterized by a shallower depth of the heat-affected zone. Structural changes in the plasma cutting zone of AA2024 alloy specimens with a thickness of 12 mm differ from those previously described for titanium alloy (Fig. 8). All samples under study are characterized by the presence of a metal melting zone, a heat-affected zone, and a base metal with an unchanged structure. For the most of the specimens, it is possible to identify macrogeometric distortions and the flowed metal formation from the material remelted in the cutting cavity and accumulated in the lower part of the cut.
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