Ultrafine-grained (UFG) samples of PT-3V near-α titanium alloy were subjected to diffusion welding using the Spark Plasma Sintering system. It has been shown that the destruction of welded UFG samples under hot salt corrosion (HSC) is two-staged – first, intercrystalline corrosion is manifested, which then graduates to pitting corrosion. It has been established that the corrosion resistance of weld joints is determined by vanadium concentration at the grain boundaries, the size and volume ratio of β-phase particles and the presence of pores in the weld joints. It has been shown that welded UFG samples possess higher hardness and corrosion resistance than coarse-grained samples.

t—The diffusion welding of ultrafine-grained pseudo-α-titanium Ti–4.73% Al–1.88% V alloy specimens has been performed by spark plasma sintering. It has been shown that the destruction of welded joints in the ultrafine-grained (UFG) specimens under hot salt corrosion (HSC) conditions has a two-stage character: intercrystallite corrosion (ICC) is developed at the first stage to turn into pitting corrosion at the following stage. It has been established that the resistance to intercrystallite corrosion is governed by the concentration of vanadium on grain boundaries, the size and volumetric content of β-phase particles, and the existence of pores in a welded joint. It has been demonstrated that the welded joints of the ultrafine-grained specimens have higher hardness and resistance to intercrystallite corrosion as compared to coarse-grained specimens.

Ultrafine-grained (UFG) samples of PT-3V pseudo-α titanium alloy were subjected to diffusion welding through spark plasma sintering. It has been shown that the destruction of welded UFG samples under hot salt corrosion (HSC) is two-staged: first, intercrystalline corrosion (ICC) is manifested, which then graduates to pitting corrosion. It has been established that the corrosion resistance of the weld joints is determined by the concentration of vanadium at the grain boundaries, the size and volume ratio of the β-phase particles, and the presence of pores in the weld joints. It has been shown that welded UFG samples possess a higher hardness and resistance to ICC than coarse-grained samples.

The paper presents results of studying alpha- and near-alpha-titanium alloy (PT3V, PT7M, and VT1-0) samples. The samples were obtained according to standard procedures of thermal deformation processing. The alpha- and near-alpha titanium alloys are used for manufacturing heat exchange equipment for modem nuclear power plants. Electrochemical polishing and acid treatment of the alloy sample surface leads to a visible decrease in the width of diffraction peaks. it also leads to a clearer representation of the "fine structure" of diffraction peaks. This indicates the presence of at least two crystalline phases. Electrochemical polishing after mechanical grinding to 1 mu m roughness shows different diffraction patterns depending on the length of the polishing period.

Titanium alloys are widely used as materials for the elements of nuclear power plants, which are subject to high reliability requirements. The goal of the study is to develop X-ray diffraction analysis of the phase composition of α - and near- α -titanium alloys. Surface treatment of the samples of titanium alloys PT-3V, PT-7M and VT1-0 was carried out by mechanical, electrochemical polishing and chemical etching. It is shown that PT-3V and PT-7M alloys are characterized by a mixed structure consisting of α - and α ’-phases with precipitation of submicron particles of the β -phase along the grain boundaries. The results of X-ray diffraction analysis of the samples obtained on an X-ray diffractometer Shimadzu XRD-7000 (Cu K α radiation) were compared with the data of metallography and electron microscopy. It is shown that the results of X-ray diffraction analysis strongly depend on the method, quality and duration of the surface treatment of the samples. Electrochemical polishing and acid treatment reduce the width of diffraction peaks and lead to a more pronounced manifestation of their «fine» structure thus demonstrating the presence of at least two crystalline phases in the alloys. «Splitting» of the main X-ray peaks of titanium is a consequence of the fine structure of primary X-ray radiation ( K α 1,2 -doublet). Presence of «fine» structure of X-ray peaks and correlation between the intensities of different peaks appears to depend essentially on the mode and quality of surface treatment of the titanium alloy thus reducing the reliability of quantitative analysis of the phase composition of titanium alloys without verification of the results by direct methods of studying alloy structure.