OBRABOTKAMETALLOV technology Vol. 27 No. 3 2025 Fig. 2. Calorimetric curves of ingots 1, 2, and 3 of TiNiHf SMA use homogenization annealing, and ingots 2 and 3 were deformed in the as-cast state. Homogenization annealing was therefore excluded from the production process for TiNiHf SMA semi-finished products to optimize the technology. Production of TiNiHf SMA semi-finished products Before deformation, the ingots were cut into two parts. The resulting ingots had the following dimensions: 2-1 – 10.4 × 18.5 × 53.1 mm and 2-2 – 10.4 × 18.5 × 77.1 mm; 3-1 – 9.8 × 17.8 × 52.1 mm and 3-2 – 9.8 × 17.8 × 76.7 mm. Hot deformation of ingots 2-1 and 3-1 was first performed by longitudinal rolling at 850 °C. The samples were preheated for 15 minutes without a protective atmosphere to improve rolling workability, unlike previous studies [23] where heating was in a protective argon atmosphere, with 3–5 minute reheating before each pass. The relative strain in one pass was kept below 15%. Hot rolling of ingot 2-1 produced a sheet with dimensions 2.2 × 27.5 × 167.9 mm. However, ingot 3-1 fractured after only 2 passes, accumulating a relative strain of 12%. Considering the lack of distinct peaks on the calorimetric curves, the melting of the similar ingot 1 during homogenization annealing, and the alloy’s low workability, it’s likely that ingot 3 contained many undesirable secondary phases formed during cooling after melting or during heating for rolling. This suggests that the alloy with 5 at.% Hf has better workability than the alloy with 10 at.% Hf. Fig. 3 shows photos of the sheet from ingot 2-1 and the fractured ingot 3-1.
RkJQdWJsaXNoZXIy MTk0ODM1