| Summary: | In this study the influence of scandium on the structural and phase state of the Ti-Al alloy obtained by the method of “Hydride Technology” (HT). The Rietveld method has allowed for determining the content of basic phases of the 49at.%Ti-49at.%Al-2at.%Sc system. By means of the methods of transmission electron microscopy (TEM) and X-ray spectral microanalysis, it has been established that scandium additives into the Ti-Al system result in the change of the quantitative content of phases in local regions of the structure. The Ti<sub>2</sub>Al<sub>5</sub> phase has been found, and Ti<sub>2</sub>Al has been absent. In the morphology of substructures Ti-Al and Ti-Al-Sc there are lamellar structures or lamellae; the peculiarities of the distribution, fraction and size of which are influenced by scandium additives. The average width of Al-rich lamellae has been 0.85 µm, which is four times greater than that for the Ti-Al system (0.21 µm). For Ti-rich lamellae of the sample of the Ti-Al-Sc alloy, the average width of the lamellae has been 0.54 µm, and for Ti-Al it has been 0.34 µm. Based on the obtained data, a scheme of the distribution of phases in the composition of the Ti-Al-Sc alloy in the lamellar structures has been proposed. It has been established that in the Ti-Al-Sc system there is growth of the near-surface strength relative to Ti-Al. In this way, the microhardness of the Ti-Al-Sc alloy has amounted to 1.7 GPa, that is of the Ti-Al alloy which is 1.2 GPa.
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