OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 molten pool is concentrated in the immediate vicinity of the welding arc, so columnar dendrites formed in the central and upper part of the weld, where the maximum heat removal is observed. The maximum length (Lmax) and width (Hmax) of dendrites in welds made at currents of 110–115 A is ≈ 1.39 mm and 0.43 mm (mode No. 3), with a decrease in current (mode No. 1), the Lmax and Hmax of dendrites are ≈ 0.99 mm and 0.23 mm, respectively (Table 3). With an increase in the welding current, the width of the zone with globular grains decreases; however, the average grain size does not change and remains within 140 ± 50 μm (Fig. 5, a, b). In welding mode No. 3, localized incomplete fusion (lack of fusion) is observed at the root of the weld (Fig. 5, a), which was confirmed previously during visual inspection of the weld appearance. Ta b l e 3 Maximum dendrite length and width (Lmax, Hmax) and average globular grain size in the weld joint metal as a function of GTAW modes Welding modes No.1 No.2 No.3 No.4 No.5 No.6 Lmax (mm) 0.99 – 1.39 0.98 0.61 1.06 Hmax (mm) 0.23 – 0.43 0.27 0.23 0.33 Average globular grain size (μm) 140 ± 50 – 140 ± 50 190 ± 40 140 ± 40 130 ± 45 а b c d e Fig. 5. EBSD maps in cross-section of Ti–Al–Nb–(Zr, Mo)–Si alloy weld joints, obtained by GTAW according to: a – mode No. 1; b – mode No. 3; c – mode No. 4; d – mode No. 5; e – mode No. 6
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