OBRABOTKAMETALLOV Vol. 27 No. 3 2025 technology diffractometer with CuKα radiation at 2θ angles from 35 to 47° [18, 24]. Vickers hardness was measured at room temperature using a LECOM 400-A hardness tester under a 1 N load to determine mechanical properties. Result and Discussion Initial TiNiHf SMA Ingots Fig. 1 shows the general appearance of the ingots produced by electron beam melting. Table 1 presents the mass, dimensions, and chemical composition of the ingots. a b c Fig. 1. Photographs of ingots 1 (a), 2 (b), and 3 (c) of TiNiHf SMA after vacuum arc melting with 8-fold remelting Ta b l e 1 Weight, dimensions and estimated composition of the TiNiHf ingots Ingot No. Weight, g Dimensions, (h × b × L) mm Chemical composition mass % at.% Ti Ni Hf Ti Ni Hf 1 148.84 9.5 × 18.1 × 137.5 28.87 44.23 26.90 40.0 50.0 10.0 2 150.15 10.4 × 18.5 × 136.9 36.03 49.06 14.92 45.0 50.0 5.00 3 149.12 9.8 × 17.8 × 137.5 28.87 44.23 26.90 40.0 50.0 10.0 After melting, the martensitic transformation temperature range (TRMT) of the ingots was analyzed using differential scanning calorimetry (DSC). Characteristic calorimetric curves are shown in Fig. 2. DSC analysis of samples fromingots 1 and 3 showed no peaks for either forward or reverse transformations within the temperature range studied. Ingot 2, however, showed a reverse MT with starting and finishing temperatures of 63 °C and 124 °C, respectively. This wide temperature range is typical for as-cast ingots due to potential internal stresses and segregation. To improve homogeneity, ingot 1 was initially subjected to a 12-hour homogenization annealing at 1,100 °C in vacuum. However, the ingot melted during annealing, possibly due to the formation of phases with lower melting temperatures during cooling after melting. Therefore, it was decided not to
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