A hot salt corrosion (HSC) test was performed on the fine-grained titanium alpha-alloy Ti-2.5Al-2.6Zr (Russian industrial alloy PT-7M). The ultrafine-grained (UFG) microstructure in the titanium alpha-alloy was formed via cold Rotary Swaging. The grain size and volume fraction of the recrystallized microstructure in the alloy were varied by choosing appropriate annealing temperatures and times. The microstructure and corrosion resistance of UFG alloys were studied after 30 min of annealing at 500-700C and after 1000 h of annealing at 250C. Metallographic studies were carried out to investigate the effects of annealing on the nature and extent of corrosive damage in the titanium alpha-alloy Ti-2.5Al-2.6Zr. After HSC tests, surface analyses of the titanium alpha-alloy samples were conducted using X-ray diffraction and electron microscopy. During the HSC testing of the titanium alpha-alloy Ti-2.5Al-2.6Zr, a competitive interaction between intergranular corrosion (IGC) and pitting corrosion was observed. To the best of our knowledge, it was shown for the first time that annealing affects the relationship among the IGC, pitting corrosion and uniform corrosion rates of the titanium alloy. Prolonged low-temperature annealing at 250C resulted in a more pronounced increase in the uniform corrosion rate than short-term high-temperature annealing for 30 min at 500-700C. An in-depth analysis of the effect of the structure and phase composition of the grain boundaries on the susceptibility of the alpha-alloy Ti-2.5Al-2.6Zr to HSC was conducted.

The corrosion-fatigue strength in 3 % aqueous NaCl solution and the resistance against hot salt corrosion (HSC) of the fine-grained near-alpha alloy Ti-5Al-2V (Russian analogue of Grade 9 titanium alloy with increased aluminium content) have been studied. The properties of the Ti-5Al-2V alloy in the coarse-grained state, in the fine-grained state after cold Rotary Swaging (RS), in the partly recrystallized state and in the fully recrystallized state have been investigated. The mechanical properties of the alloy were characterised using compression tests and microhardness measurements. The effects of RS, the annealing temperature, the time on the characteristics of corrosion destruction of the surface and the composition of the products of the HSC were studied. RS was shown to increase the depth of the intergranular corrosion defects, whereas recrystallization annealing promoted an increase in the corrosion resistance of the Ti-5Al-2V titanium alloy. The parameters of the Basquin equation for the corrosion-fatigue curves for the near-alpha Ti-5Al-2V alloy in the coarse-grained state, in the severely strained state and after recrystallization annealing were determined for the first time. An effect of non-monotonous dependencies of the slopes of the corrosion-fatigue curves for the strained near-alpha Ti-5Al-2V alloy on the recrystallization annealing temperature has been observed.

The quality of water-chemistry management in the secondary loop on ships with nuclear power plants (TNPPs) was analyzed by studying resin samples taken from ion-exchange filters. The collected data were compared with the results of tests performed on a TNPP bench. On the basis of the analysis and comparisons, recommendations were developed to improve the water-chemistry regime management in the second loop of transport nuclear power plants.

The effect of severe plastic deformation by rotary forging on the mechanical properties and the corrosion resistance of a pseudo-α-titanium PT-7M alloy is studied. The corrosive character of fracture the fine-grained alloy under hot salt corrosion (HSC) conditions is found to change: pitting corrosion at the onset of recrystallization processes changes into intercrystalline corrosion. The HSC resistance of the fine-grained PT-7M titanium alloy is shown to depend on the structure–phase state of grain boundaries, whose intense migration with developing recrystallization leads to “sweeping out” of corrosion-hazardous alloying elements (aluminum, zirconium) from the crystal lattice of the titanium alloy.

The study focuses on corrosion fatigue processes taking place in an ultrafine-grained (UFG) near-a-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M) used in nuclear engineering. UFG structure formed with Rotary Swaging is found to increase resistance to corrosion fatigue. Parameters of the Basquin's equation are defined and the slope of the fatigue curve Sa-lg(N) is shown to depend (nonmonotonic dependence) on the UFG alloy annealing temperature. This effect can be explained with the patterns of microstructural evolution in a UFG alloy PT7M during annealing: (1) reduced density of lattice dislocations, (2) precipitation and dissolution of zirconium nanoparticles, (3) release of a''-phase particles causing internal stress fields along interphase (a-a'')-boundaries, and (4) intensive grain growth at elevated annealing temperatures. It is shown that the fatigue crack closure effect manifested as changing internal stress fields determined using XRD method may be observed in UFG titanium alloys.

The research has been conducted into the impact that structural-phase state of grain boundaries in α-titanium alloy Ti-5Al-2V has on strength, plasticity and susceptibility to intercrystalline corrosion (ICC). It is found that during Equal Channel Angular Pressing (ECAP) performed at elevated temperatures there is a change in local concentration of alloying elements (aluminum, vanadium) along α-Ti grain boundaries. The current study proves that by controlling the structure of α-titanium alloy Ti-5Al-2V through ECAP it is possible to enhance its strength and resistance to hot salt intercrystalline corrosion. Plasticity of ultrafine-grained (UFG) alloy samples at room temperature is comparable with plasticity of a coarse-grained material, while plasticity of an UFG alloy at elevated temperatures is 2–3 times bigger than plasticity of a coarse-grained material.

The influence of the structural-phase state of grain boundaries in a Ti4Al2V (commercial PT3V grade) pseudo-alpha-titanium alloy on its susceptibility to hot-salt intergranular corrosion (IGC) has been studied. It is established that IGC-tested alloy samples exhibit corrosion-induced defects of two types. More extended defects of the first type occur at the V-rich boundaries of coarse grains, while short defects of the second type reside at the grain boundaries with composition close to that of the grain body. The existence of the two types of IGC defects is explained by the classical theory of galvanic microcouples (microcells), according to which the IGC intensity is proportional to the difference of corrosion-active impurity concentrations between the grain boundary and body.

The influence of severe plastic deformation on the structural-phase state of grain boundaries in a Ti–4Al–2V (commercial PT3V grade) pseudo-alpha-titanium alloy has been studied. It is established that increase in the strength, plasticity, and corrosion resistance of this alloy is related to the formation of an ultrafine- grained structure. In particular, it is shown that an increase in the resistance to hot-salt intergranular corrosion is due to diffusion-controlled redistribution of aluminum and vanadium atoms at the grain boundaries of titanium formed during thermal severe plastic deformation.