OBRABOTKAMETALLOV Vol. 26 No. 4 2024 TECHNOLOGY а b c Fig. 8. Change in microhardness in the surface layers of bronze Cu-9 Al-2 Mn (a) and the results of X-ray analysis of the base metal (b) and the cut surface (c) similarly shaped protrusions in the central part of the cut (marked as 1 in Fig. 9, d). The primary reason for the distinctive morphology of the titanium alloy cut surface is the oxidation of the surfaces, which results in the formation of a continuous oxide layer, as confi rmed by SEM and EDS analysis (Fig. 9, e, f). According to EDS and X-ray diff raction (XRD) analysis, the main oxide phase is Ti₂O (Fig. 11, d). The surface layer may also contain dendritic structures that formed during the crystallization of the oxide (marked as 2 in Fig. 9, e), as well as microcracks (marked as 3 in Fig. 9, f), the formation of which occurred during the cooling of the material after cutting. Structural and chemical analysis of the material shows that the melt zone is stable and that oxidation extends across nearly the entire surface (Fig. 10, a; Fig. 11, b), penetrating up to 0.5 mm into the lower part of the cut. The material in the cross-section is also characterized by the presence of a melt zone, a heat-aff ected zone (HAZ), and the base metal (Fig. 10, a-d). During the melting of titanium and its oxides, dendritic structures form. Both the base metal and the heat-aff ected zone exhibit alpha and beta-phase lamellae, as a b c d e f Fig. 9. Images of the cut surface of titanium alloy Ti-5 Al-5 Mo-5 V obtained by laser scanning (a–c) and scanning electron (d–f) microscopy
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