OBRABOTKAMETALLOV Vol. 24 No. 4 2022 technology Fig. 7. Macro- and microstructure of typical package specimen of two sheets of titanium alloy with a thickness of 5 mm after plasma cutting: a – macrostructure; b–e – microstructure of specific zones; f–i – microhardness variation; 1 – base metal; 2 – heat-affected zone; 3 – melting zone; 4 – zone boundary; 5–8 – areas of microhardness testing The heat-affected zone in specimens is represented by an almost undeformed structure of the base metal with enhanced etchability relative to it (Fig. 8, a–c). The size of the heat-affected zone is about 100–200 µm in the upper part and 600–2,000 µm in the bottom part, with the lowest values for mode No. 2. All specimens are characterized by an identical structure in the initial state (Fig. 8, d). In the melting zone a typical structure with dendritic texture is formed when molten metal flows down the cut surface (Fig. 8, g). Due to the high rate of crystallization of the metal on the cut surface, formation of a fine dendritic texture and defects in the form of cracks occurs (Fig. 8, e).
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