Ekaterina N. Stepanova

Structure and mechanical properties of ultrafine-grained Ti-6Al-4V alloy made by applying reversible hydrogen alloying

The special features of the ultrafine-grained structure forming in a Ti-6Al-4V alloy with the use of a method combining severe plastic deformation and reversible hydrogen treatment are studied by electron microscopy and X-ray diffraction analysis. Martensite and the α ↔ β phase transformations due to hydrogen presence are found to promote structure refining during severe plastic deformation of the alloy. This makes it possible to decrease the degree of deformation required for obtaining the ultrafine-grained structure with the size of elements of 0.1–0.5 μm. Formation of the ultrafine-grained structure in a Ti-6Al-4V alloy is shown to lead to growth of its strength properties by approximately a factor of 1.5, an increase in the hydrogen embrittlement resistance, and a decrease in the temperature transition to the superplastic state by 200–300 K.

Effect of Pulsed Electron Beam Treatment and Hydrogen on Properties of Zirconium Alloy

The paper presents the results of the pulsed beam effect on the structure and phase composition of zirconium alloy. Such treatment is demonstrated to lead to forming of complex morphology martensite in the surface layer of the alloy. The processes of hydrogen absorption by zirconium alloy with modified surface have been studied. Modification of the samples is found to reduce the amount of hydrogen, absorbed by the volume of zirconium alloy during hydrogenation.

Effect of Hydrogen on the Development of Superplastic Deformation in the Submicrocrystalline Ti–6Al–4V Alloy

Hydrogenation effect on the development of superplastic deformation in the submicrocrystalline Ti–6Al–4V alloy at temperatures (0.4–0.5)Тmelt is investigated. Hydrogenation of the submicrocrystalline Ti–6Al–4V alloy to 0.26 mass% during superplastic deformation is found to result in solid solution strengthening, plastic deformation localization, and as a consequence, decrease of the deformation to failure. Possible reasons for the decrease of the flow stress and increase of the deformation to failure in the submicrocrystalline Ti–6Al–4V–0.26H alloy during deformation under conditions of superplasticity and simultaneous hydrogen degassing from the alloy are discussed.

Properties of the VT1-0 titanium surface modified by a pulsed ion beam

The physicomechanical properties of the VT1-0 titanium surface modified by a pulsed carbon ion beam at a pulse duration of 80 ns, an energy of 200 keV, a current density of 120 A/cm2, an energy density of 1.92 J/cm2, and various numbers of pulses (four regimes) are studied. Irradiation by the beam leads to hardening of a 1.8-μm-thick surface layer in titanium, a decrease in the hydrogen sorption rate, a decrease in the grain size, and the formation of twins.

Effect of hydrogen on the structural and phase state and defect structure of titanium alloy

Effect of hydrogen on the structural and phase state of the fine- and ultrafine-grained structure of two-phase (alpha + beta) titanium Ti-6Al-4V alloy was investigated by the methods of electron microscopy and X-ray diffraction analysis. The defect structure of the fine- and ultrafine-grained samples before and after hydrogen treatment was studied by the implemented Positron lifetime technique. Hydrogenation is found to result in minor structural and phase changes both in fine- and ultrafine-grained samples. It is shown that defect structure of samples depends on the structural state and hydrogen presence.

Research of Hydrogenation and Dehydrogenation Effect on the Structural and Phase State of the Titanium Alloy

Effect of hydrogen on the structural and phase state of the fine-grained and submicrocrystallinestructure of two-phase (alpha + beta) titanium Ti-6Al-4V alloy was investigated by the methods of electron microscopy and X-ray diffraction analysis. Hydrogenation is found to result in minor structural and phase changes both in fine-grained and submicrocrystalline samples.The use of electron beam exposure combined with heating for hydrogen release in the Ti-6Al-4V alloy is shown to reduce degassing time and decrease the hydrogen concentration to the values closed to the engineering standards for the Ti-6Al-4V alloys.

Effect of nonequilibrium hydrogen release in the ultrafine-grained Zr-1Nb alloy under the electron beam exposure

The evolution of structural and phase state and hydrogen release from the ultrafine-grained hydrogenated zirconium Zr-1Nb alloy during vacuum annealing and electron beams exposure were studied. The use of electron beam irradiation for hydrogen degassing is shown to decrease the temperature of active hydrogen release by 100-200 K and/or reduce the time required for hydrogen degassing from the alloy to concentrations corresponding to technical standards.

Effect of deformation and heat treatment on the structure, the mechanical properties, and the fracture characteristics of an ultrafine-grained Zr–1Nb alloy

The effect of cold working and annealing for various times on the structure, the mechanical properties, and the fracture characteristics of an ultrafine-grained Zr–1 wt % Nb alloy after three-dimensional pressing is studied. Possible causes for increasing the thermal stability of the strength properties of the ultrafine-grained Zr–1 wt % Nb alloy during prerecrystallization annealing after additional cold working by rolling are discussed.