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The paper studies the effect of electrolytic hydrogen charging on the plastic flow, strength properties, ductility, and fracture mechanisms in austenitic stainless steels Cr17Ni13Mo3C0.01, Cr18Ni10TiC0.12, and Cr18Ni9C0.17 with different stacking fault energies. The investigated steels are subjected to warm ABC-pressing and thermomechanical processing, including cold rolling and annealing, to produce the ultrafine-grained structure of different morphologies, such as ultrafine-grained (submicrocrystalline), misoriented grain-subgrain and mixed (grain and subgrain) structures of submicron scale. The strength properties of the steels after warm pressing and rolling with annealing exceed 3.5–6.0 times the properties of the quenched steels with coarse-grained structure. Electrolytic hydrogen charging of the studied steels with submicron-sized structure reduces the yield strength irrespective of the grain/subgrain size, structure, steel composition, and its stacking fault energy. The formation of a highly defective grain-subgrain structure with high dislocation density suppresses the effect of hydrogen embrittlement in Cr17Ni13Mo3C0.01 and Cr18Ni10TiC0.12 steels, in which no or a small volume fraction of strain-induced α′ martensite forms in tension. The tempering of the highly defective structure and the formation of a large fraction of high-angle misorientations in the stable Cr17Ni13Mo3C0.01 steel enhances the effect of hydrogen embrittlement in the specimens as compared to the specimens with a grain-subgrain structure with a high density of dislocations and low-angle boundaries. The hydrogen embrittlement effects are most pronounced in ultrafine-grained (submicrocrystalline) Cr18Ni10TiC0.12 and Cr18Ni9C0.17 steels with predominantly grain structure, which undergo induced γ→α′ phase transformation.

This paper studies the effect of electrolytic hydrogen charging on the plastic deformation and fracture of Hadfield steel single crystals oriented for tension along the ‹111› and ‹144› directions, which the major deformation mechanism is mechanical twinning. Electrolytic hydrogen charging for five hours at a current density of 100 A/m2 slightly affects the stages of plastic flow, deformation mechanism, and the value of uniform elongation of ‹111› and ‹144› single clreystals. Hydrogen saturation causes shear microlocalization and a decrease of the strain hardening coefficient in twinning in one system, but slightly affects the strain hardening characteristics in multiple twinning. Hydrogen charging increases the fraction of the brittle component on fracture surfaces and leads to microand macrocracking near the fracture zone on the lateral surface of deformed specimens. It has been found experimentally that the stress relaxation rate in loaded ‹111› single clreystals after hydrogen saturation decreases. Mechanisms of describing this phenomenon have been proposed.

The effect of annealing on the evolution of an ultrafine-grain structure and carbides in a 06MBF steel (Fe–0.1Mo–0.6Mn–0.8Cr–0.2Ni–0.3Si–0.2Cu–0.1V–0.03Ti–0.06Nb–0.09C, wt %) has been studied. The grain–subgrain structure (d = 102 ± 55 nm) formed by high-pressure torsion and stabilized by dispersed (MC, M3C, d = 3–4 nm) and relatively coarse carbides (M3C, d = 15–20 nm) is stable up to a temperature of 500°C (1 h) (d = 112 ± 64 nm). Annealing at a temperature of 500°C is accompanied by the formation in regions with a subgrain structure of recrystallized grains, the size of which is close to the size of subgrains formed by high-pressure torsion. The average size and distribution of dispersed particles change weakly. The precipitation hardening and the increase in the fraction of high-angle boundaries in the structure cause an increase in the values of the microhardness to 6.4 ± 0.2 GPa after annealing at 500°C as compared to the deformed state (6.0 ± 0.1 GPa). After 1-h annealing at 600 and 700°C, the microcrystal size (d = 390 ± 270 nm and 1.7 ± 0.7 μm, respectively) increases; the coarse M3C (≈ 50 nm) and dispersed carbides grow by 5 and 8 nm, respectively. The value of the activation energy for grain growth Q = 516 ± 31 kJ/mol upon annealing of the ultrafine-grained steel 06MBF produced by high-pressure torsion exceeds the values determined in the 06MBF steel with a submicrocrystalline structure formed by equal-channel angular pressing and in the nanocrystalline α iron.

The structure of EK-181 (RUSFER-EK-181, low-activation) and ChS-139 12% Cr ferritic–martensitic steels is investigated and their mechanical properties are tested after long-term (13500 h) aging at 450 and 620°C. The microstructure of the steels exhibits a high thermal stability, which provides the retention of their initial short-term mechanical properties at test temperatures.

The thermophysical properties (specific heat, thermal diffusivity, thermal conductivity, linear thermal expansion coefficient, density) of 12% chromium ferritic–martensitic steels EK-181 (RUSFER-EK-181) and ChS-139 and the structure–phase transformations that occur in them upon heating and cooling in the temperature range 20–1100°C are studied. The temperatures of the start and finish of the α → γ and γ → α transformations in these steels and the Curie temperature are determined by differential scanning calorimetry. Peaks in the temperature dependence of the specific heat and jumplike changes in the linear thermal expansion coefficient and the density and the minimum of thermal diffusivity are detected in the α → γ transformation range. Specific heat peaks, thermal conductivity minima, and inflection points in thermal diffusivity curves are also observed near the Curie temperature.

Mechanisms of structure fragmentation and strengthening of single crystals of a Hadfield steel after warm torsion under high-pressure torsion (HPT) and subsequent annealing in a temperature range of 400–800°C have been studied. Multiple twinning and formation of ultrafine carbides upon HPT at 400°C (P = 5 GPa) promote rapid fragmentation of the microstructure. They are responsible for the high mechanical properties of the steel after HPT and the thermal stability of the microstructure up to an annealing temperature of 500°C.

The effect of heat treatment conditions on the microstructure and phase composition of a lowactivated high-temperature ferritic-martensitic EK-181 steel (Fe-12Cr-2W-V-Ta-Ba) is studied. Additional thermal cycling about the austenite-martensite phase transition temperature between quenching and tempering hinders the formation of fine interstitial phases, decreases the phase transformation-induced hardening intensity, retards the formation of a substructure with continuous misorientations, and decreases the brittle-ductile transition temperature.

The properties of steel after equal channel angular pressing (ECAP) and subsequent high-temperature annealing are investigated. ECAP leads to an increase in strength properties of steel, to a decrease in plasticity, and to localization of plastic strain. High strength properties and localization of plastic flow are retained up to an annealing temperature of 500°C. Influence of ECAP and further annealing on deformation and fracture mechanisms is discussed.

Results are given of the investigation of mechanical properties, microstructure, and phase composition of low-carbon ferritic-pearlitic steel 10G2FT (Fe-1.12Mn-0.08V-0.07Ti-0.1C) after equal-channel angular pressing and subsequent high-temperature annealing at temperatures of 500–700°C. It has been shown that the predominantly submicrocrystalline structure formed during the equal-channel angular pressing possesses high thermostability up to a temperature of 500°C. The contribution of age hardening to the strengthening of steel 10G2FT during the equal-channel angular pressing and to the stabilization of the submicrocrystalline structure to high annealing temperatures is discussed.

The deformation mechanism and the character of fracture of 〈111〉 austenitic Hadfield steel single crystals are studied during tension in the temperature range 77–673 K by scanning and transmission electron microscopy. It is found that a change in the fracture mechanism from ductile to brittle fracture according to the fractography criterion takes place at a higher temperature than that determined from a change in the elongation to failure of the single crystals. The ductile-to-brittle transition in the Hadfield steel single crystals is shown to be related to a high level of deforming stresses induced by solid-solution hardening and to mechanical twinning.

Results are presented of the investigation of mechanical properties, microstructure, and phase composition of low-carbon steel 10G2FT (Fe-1.12Mn-0.08V-0.07Ti-0.1C) before and after equal-channel angular pressing (ECAP). It has been established that the ECAP of steel 10G2FT at T = 200°C in the case of the ferritic-pearlitic state and at T = 400°C in the case of the martensitic state leads to the formation of a predominantly submicrocrystalline structure with an average size of structural elements of approximately 0.3 μm, causes an increase in the strength properties, a decrease in the plasticity, and the localization of plastic flow. It has been experimentally shown that the initially martensitic structure after ECAP causes higher strength properties in comparison with the ferritic-pearlitic structure.

Transmission electron microscopy and X-ray diffraction have been used to experimentally study the mechanism of deformation of Hadfield steel single crystals oriented for tension along \( [\bar 111], [\bar 144]\) , and [011] directions. It has been established that at T = 23 ° C starting from the early degrees of deformation (ɛ > 0.5%) the process of plastic flow in single crystals of these orientations is connected with the development of predominantly mechanical twinning. The influence of the number of operative shear systems on the rate of strain hardening has been shown.

The structural and phase transformations which take place in low-carbon 0.1% C-Mn-V-Ti steel during deformation by high pressure torsion (HPT) and subsequent heating have been studied using transmission electron microscopy and X-ray structural analysis methods. Whatever the initial state, be it ferritic-pearlitic or martensitic (obtained by quenching from 950°C and 1180°C), HPT at room temperature leads to the formation of a nanosized oriented grain-subgrain structure. The average size of the elements of the grain-subgrain structure in the 0.1% C-Mn-V-Ti steel after severe plastic deformation is larger in the initially ferritic-pearlitic state (95 nm) than in the initially martensitic states (65 and 50 nm after quenching from 950°C and 1180°C, respectively). It is shown that quenching from 950°C and 1180°C causes the formation of the martensite of different fineness, providing, in turn, nanostructures of different dimensions and different levels of the strength properties after HPT. Quenching from 1180°C is conducive to a higher thermal stability of the HPT-induced nanocrystalline structure of the 0.1% C-Mn-V-Ti steel on account of the larger amount of vanadium carbide precipitates. It is found that HPT leads to a considerable increase in the microhardness of the 0.1% C-Mn-V-Ti steel as compared to its microhardness in the initial state (more than 3 times as high in the ferritic-pearlitic state and more than 2 times as high the initially martensitic states).