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[References: p. 447 (19 tit.)]

The thermal stability of Ti-45Nb powder obtained via mechanical alloying of pure components Ti and Nb using an AGO-2C high energy planetary ball mill was studied. To evaluate the structure and phase transformations in the material, scanning and transmission electron microscopic studies and x-ray diffraction analysis were carried out. Mechanical alloying of titanium and niobium powders occurs under the conditions of severe plastic deformation and leads to the homogenization of initial components. As a result, an alloy with the structure consisting of a mixture of different grains is formed. This mixture of nanosized grains consists of the main ?-TiNb phase and metastable ?- and ?"-phases. The presence of metastable phases, large amount of interfaces, lattice distortions of the main phase indicate the presence of high internal energy stored in the material. By means of differential scanning calorimetric analysis it was found that structural and phase transformations occurred during heating of the powder up to temperatures of about 500°C and 700°C. During annealing at 500°C the mechanically alloyed powder loses the metastable ?"-phase while the ?-phase becomes equilibrium. At the same time, the process of recrystallization nuclei formation starts in the structure. The annealing at 700°C does not change the phase composition of the alloy. The exothermal effect observed at this temperature is related to structural transformations in the alloy, in other words, to the recrystallization of plastically deformed material. Basing on the results obtained it was concluded, that the upper limit of the thermal stability of mechanically alloyed Ti-45Nb powder does not exceed 500°C.