OBRABOTKAMETALLOV TECHNOLOGY Vol. 26 No. 4 2024 BM HAZ FZ a BM BM HAZ FZ FZ b c d BM HAZ FZ FZ FZ Fig. 4. Macrostructure (a), images of the microstructure obtained by optical (b–d) and scanning electron (e–g) microscopy of a specimen of aluminum alloy Al-6 Mg e f g and is also observed during welding by various methods. X-ray diff raction (XRD) analysis indicated that no phase composition changes occur in the surface layers, and the structure remains Al(Mg) (Fig. 5, c, d). Due to the removal of work hardening and the depletion of magnesium in the surface layers of the aluminum alloy, there is a signifi cant reduction in microhardness, especially in the lower part of the cut (Fig. 5, a). In the upper part of the cut, microhardness decreases from 1.21 GPa in the base metal to 1.01 GPa in the subsurface zone, whereas in the lower part, it reaches approximately 0.94 GPa near the surface. In both the upper and central regions of the cut, at a depth of 1.0 mm, the microhardness returns to values typical of the base metal, but in the lower part, it remains at 1.05 GPa. This indicates a signifi cantly greater thermal impact on the material in the lower section of the cut, due to the displacement of molten metal through this area and the diffi culty in removing it with the protective gas stream. Overall, considering the dimensional tolerances for producing blanks from plates of this thickness, both the cut distortion and the structural changes can be considered acceptable. The surface of the Cu-9 Al-2 Mn bronze after cutting also exhibits signifi cant variations in relief across the upper, lower, and central parts of the cut zone (Fig. 6, a-c). Distinct features are identifi ed, formed by the rapid solidifi cation of metal fl owing down the edge during cutting (1 in Fig. 6, d). Additionally, scanning electron microscopy (SEM) and X-ray diff raction (XRD) analysis reveal fragments of oxides (2 in Fig. 6, e) and formations resembling pores or “craters” (3 in Fig. 6, f). The oxidation of the surface is patchy, and a continuous oxidized layer does not form.
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