OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology additional blowing into the weld root (Fig. 2, a). The shielding gas flow rate was 12 L/min, and the gas for blowing rate was 2 L/min. The workpieces for GTAW (25×15×2 mm) were cut from the forged piece using VL400Q and VL600Q wire electrical discharge machines (Sodick, China). The surface of the workpieces was prepared before GTAW using abrasive paper: the abutting surfaces were ground with FEPA P1000 (18 μm, GOST No. M20) abrasive paper, and the remaining surfaces were ground with FEPA P220 (68 μm, GOST No. 6) abrasive paper. Welding of the 2 mm thick plate workpieces was performed in a butt joint configuration. Welding was performed using speedup welding condition. Low- and high-frequency pulsed welding was also used in the study (Table 2). A feature of gas tungsten arc welding using low- and high-frequency pulsing is that additional pulses with a specified amplitude are superimposed on the effective constant welding current, forming energy peaks that exceed the background current. At the same time, the formation of the welds occurs sequentially in a droplet mode, which eliminates metal spatter and allows for the production of thin-walled welded joints without burn-through. Arc ignition was performed on the edge of the workpieces being welded due to the absence of runoff plates. The welding current range was 80…150 A. Fig. 1. Initial microstructure of the Ti–Al–Nb–(Zr, Mo)–Si alloy a b c Fig. 2. GTAW welding fixture (a), specimens for mechanical testing (b) and microhardness testing specimens (c) of the welded joint of Ti–Al–Nb–(Zr, Mo)–Si alloy Specimens for uniaxial tensile testing, microstructural analysis, and microhardness testing were ground with silicon carbide-based abrasive papers FEPA P 220–2000 (Struers, Denmark) on a grinding and polishing machine (Chennai Metco BAINPOL, India). The polishing was carried out on a 200 mm polishing wheel made of MD-Nap cloth from Struers using O.P.S (MetCata, Germany) or OP-S (Struers, Denmark) 0.05 μm suspension. To determine the mechanical properties of the welded joints made of Ti–Al–Nb–(Zr, Mo)–Si alloy, uniaxial tensile tests were performed using a 5882 universal testing machine (Instron, USA). The test temperature corresponded to room temperature. The strain rate during tensile testing was set to 10–4 s–1. The shape and dimensions of the uniaxial tensile test specimens are shown in Fig. 2. The microhardness was measured in the cross-section of the welded joints using a 402MVD microhardness tester (Instron, Netherlands) equipped with a diamond indenter. The load applied to the indenter corresponded to 200 g with a holding time of 10 sec. The distance between measurements was 100 μm. The measurement was carried out along one line in the center of the specimen, i.e., at a depth of 1 mm, as shown in Fig. 2, c.
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