OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 a b Fig. 7. Results of uniaxial tensile testing of Ti–Al–Nb–(Zr, Mo)–Si alloy weld joints as a function of GTAW modes: a – tensile stress-strain diagram; b – graph of mechanical properties In welded joints obtained with direct current welding, the joints perform extremely low ductility and strength properties. In welds obtained in mode No. 1, a localized lack of fusion was observed, which led to a decrease in strength to less than 80 %. In addition, the strength of the welded joint obtained in mode No. 3 is ≈ 40 % of the strength of the base metal. This is due to the fact that in this mode, the maximum grain size of the dendritic structure of the FZ was found, which exceeds by 1.5 times the maximum sizes of dendrites in the FZ of welded joints obtained with low- and high-frequency pulsed modes. When welding in mode No. 5, the decrease in the strength properties of the welded joint is possibly related to the localized lack of fusion that was found in the root part of the weld (Fig. 5, d). Fracture of the welded joints always occurs along the fusion line, and a river line pattern is visible on the fracture surface, mainly caused by the fracture of large β-grains (Fig. 8). The fracture surface of the sample welded in mode No. 6 has 2 zones, namely: a fracture area of large (dendritic structure of the FZ) and small grains. The phenomenon indicates the fracture of globular β-grains, which were formed in the root area of the weld (Fig. 8). A similar fracture pattern is observed on the remaining samples. Fig. 8. Fracture surface morphology of specimens after uniaxial tensile testing as a function of Ti–Al–Nb–(Zr, Mo)–Si alloy GTAW mode
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