E. G. Volkova

Evolution of the microstructure and microdistortions in the austenitic Cr-Ni-Ti steel during aging

Structural mechanism of intermetallic aging of the N26Kh5T3 steel at 600 and 700°C with the precipitation of particles of an ordered γ′ phase Ni3Ti of different sizes has been clarified. Neutron diffraction analysis was used to determine variations in the crystal structure, phase composition, and microdistortions in the samples depending on the aging conditions.

Evolution of the microstructure and microstresses in the 40Kh4G18F2 steel upon carbide aging

Structural mechanism of aging of the 40Kh4G18F2 steel at 600 and 700°C (precipitation of clusters and VC carbide particles) has been clarified, and its effect on the magnitude of the elastic microdeformation of the lattice of an austenitic matrix and, consequently, on the magnitude of microstresses, has been analyzed.

Fe- and co-based nanocrystalline soft magnetic alloys modified with Hf, Mo, and Zr: Magnetic properties, thermal stability, and structure. Alloys (Fe0.6Co0.4)86Hf7B6Cu1 and (Fe0.7Co0.3)88Hf7B4Cu1

Nanocrystalline alloys (Fe0.6Co0.4)86Hf7B6Cu1 and (Fe0.7Co0.3)88Hf7B4Cu1 have been investigated to obtain materials with improved thermal stability and new features. In order to make the alloys produced by melt quenching on a rotating wheel nanocrystalline, they have been subjected to heat (HT) and thermomechanical (TMechT) treatments. The effect of HT and TMechT conditions on the magnetic properties, thermal stability, and structure of the alloys has been studied. The optimal HT conditions for obtaining the minimum values of the coercive force (Hc) in the alloys have been determined. It is shown that TMechT of the alloys leads to the induced longitudinal magnetic anisotropy with the axis of easy magnetization along the long side of the ribbon in the studied temperature range of 520–620°C. It has been established that the alloys (Fe0.6Co0.4)86Hf7B6Cu1 and (Fe0.7Co0.3)88Hf7B4Cu1 are thermally unstable at temperatures above 500°C.

Magnetic properties, thermal stability, and structure of the nanocrystalline soft magnetic (Fe0.7Co0.3)88Hf2W2Mo2Zr1B4Cu1 alloy with induced magnetic anisotropy

The effect of magnitude of tensile stresses (σ) applied to the (Fe0.7Co0.3)88Hf2W2Mo2Zr1B4Cu1 alloy with refractory-metal additions during its nanocrystallization at 620°C for 20 min on the magnetic properties, structure, and thermal stability of the alloy is studied. It has been found that, during the nanocrystallization of the alloy under the effect of tensile stresses of 6–250 MPa, longitudinal magnetic anisotropy with an easy magnetization axis parallel to the long size of ribbon is induced in the alloy. The thermal stability of magnetic properties of the alloy under study has been shown to be determined by the thermal stability of induced magnetic anisotropy and to depend on the magnitude of tensile stresses applied during nanocrystallizing annealing (NA). The better thermal stability of magnetic properties has been observed for the alloy subjected to NA at σ = 170 MPa. After annealing at 570°C for 25 h, the magnetic properties of the alloy are unchanged.

Fe- and co-based nanocrystalline soft magnetic alloys modified with Hf, Mo, and Zr: Magnetic properties, thermal stability, and structure. Alloy (Fe0.7Co0.3)88Hf4Mo2Zr1B4Cu1

The alloy (Fe0.7Co0.3)88Hf4Mo2Zr1B4Cu1 is studied to obtain materials with improved thermal stability. The effect of the nanocrystallization conditions that occur during heat treatment (HT) and thermomechanical treatment (TMechT) in air at temperatures of 520–620°C on the structure of the alloy, as well as its magnetic properties and their thermal stability, is considered. Longitudinal magnetic anisotropy is shown to be induced in the alloy in the course of TMechT; the easy magnetization axis of the anisotropy is parallel to the long side of the ribbon. The alloy specimens subjected to heat and thermomechanical treatment have different magnetic characteristics. The (Fe0.7Co0.3)88Hf4Mo2Zr1B4Cu1 alloy is found to surpass the (Fe0.6Co0.4)86Hf7B6Cu1 and (Fe0.7Co0.3)88Hf7B4Cu1 alloys studied in [1] in the thermal stability of the magnetic properties. The magnetic properties of the alloy after nanocrystallization, which occurs in the course of TMechT (σ = 250 MPa) at 620°C for 20 min, hardly change during annealing at 550°C for 26 h.

Structural and phase transformations and micromechanical properties of the high-nitrogen austenitic steel deformed by shear under pressure

Using transmission electron microscopy, X-ray diffraction analysis, Mössbauer spectroscopy, microdurometry, and microindentation, the effect of large plastic deformations (through shear under pressure in Bridgman anvils) on the structure, phase composition, and micromechanical properties of high-nitrogen (1.24 wt % N) 08Kh22GA1.24 steel has been investigated. The steel was obtained by the casting method with counterpressure of nitrogen and was subjected to different heat treatments (quenching from1180°С, aging at 450 and 550°С) that form an austenitic (FCC) structure of the metallic matrix with chromium nitrides. It has been established that deformation by shear under pressure at room temperature results in the dispersion and deformation-induced partial dissolution of primary nitrides Cr2N in quenched and aged steel and in the complete (after aging at 450°С) and partial (after aging at 550°С) dissolution of secondary nitrides CrN. It has been noted that, for aged steel that contains finely dispersed secondary chromium nitrides upon shear deformation, as compared to the quenched state, the dispersion of the austenitic structure (down to nano- and submicrocrystalline states) is more intense and the enhancement in the microhardness and resistance to elastic–plastic deformations upon contact loading is more effective.

Nanocomposite films prepared by arc-plasma deposition of titanium and carbon

The composition, structure, and properties of films prepared by depositing both titanium and carbon have been investigated. It was found that the films consist of an amorphous carbon matrix with uniformly distributed therein nanoparticles of titanium carbide (less than or equal to 20 nm in size). With increasing carbon concentration above 20 wt %, the film density decreases and the microhardness of the films increases, which reflects the diamond-like nature of the amorphous constituent of the composite film.

Precipitation-hardening stainless steels with a shape-memory effect

The possibility of obtaining the shape-memory effect as a result of the γ → ε → γ transformations in aging stainless steels strengthened by VC carbides has been investigated. Regimes are given for strengthening aging (at 650 and 720°C) for stainless steels that predominantly contain (in wt %) 0.06–0.45C, 1–2V, 2–5Si, 9 and 13–14Cr. The values of reversible deformation e (amount of shape-memory effect) determined after heating to 400°C in samples preliminarily deformed to 3.5–4% vary from 0.15 to 2.7%, depending on the composition of the steels and regimes of stabilizing and destabilizing aging.

Nanocomposite vacuum-Arc TiC/a-C:H coatings prepared using an additional ionization of acetylene

The composition, structure, and properties of TiC/a-C:H coatings obtained by simultaneous vacuum-arc deposition of titanium and carbon in a low-pressure argon-acetylene medium additionally activated by a low-energy (a few hundreds of electron-volts) electron beam. The creation of conditions under which the decomposition of acetylene is provided by the ionization and dissociation of molecules due to electron impacts and by the recharging of molecules through titanium and argon ions with subsequent dissociation should favor the most complete decomposition of acetylene in a wide range of pressures. With increasing acetylene pressure, the structure of the nanocomposite coating changes: the size of TiC crystallites decreases, and the fraction of interfaces (or the fraction of regions with a disordered (amorphous) structure) increases. The application of a bias voltage leads to an increase in the sizes of TiC nanocrystallites. The coatings with a maximum microhardness (∼40 GPa) have been obtained without the action of an electron beam under an acetylene pressure of ∼0.05–0.08 Pa and the atomic ratio Ti: C ∼ 0.9: 1.1 in the coating.

Microstructure and Physicomechanical Properties of a Cu-8 at % Pd Alloy

The evolution of the structure, microhardness, and electrical resistivity has been studied during prolonged low-temperature annealings of the Cu-8 at % Pd alloy. An increase in the microhardness and electrical resistivity after annealings at temperatures of 250 and 300°C has been revealed; the preliminary deformation significantly accelerates and enhances this effect; and the X-ray diffraction patterns remain unchanged and correspond to an fcc solid solution. Using transmission electron microscopy, the state of an atomic short-range order has been detected in the quenched alloy; prolonged annealings of the deformed alloy lead to the formation of microregions of the ordered L12 phase.