Vol 58, No 9-10 (2017)

The phase composition, the hardness, the mechanical properties at room temperature, and the resistance to hot (950 – 1000°C) and warm (550°C) deformation are studied for cast deformable “light” ferritic and austenitic steels of the Fe – (12 – 25)% Mn – (0 – 15)% Al – (0 – 2)% C system alloyed additionally with about 5% Ni. The high-aluminum high-manganese low-carbon and carbonless ferritic steels at a temperature of about 0.5T_melt have a specific strength close to that of the austenitic steels and may be used as weldable scale-resistant and wear-resistant materials. The high-carbon Fe – (20 – 24)% Mn – (5 – 9)% Al – 5% Ni – 1.5% C austenitic steels may be applied as light high-strength materials operating at cryogenic temperatures after a solution treatment and as scale- and heat-resistant materials in an aged condition.

Comparative analysis of the properties of domestic and foreign sparingly alloyed titanium alloys is preformed, and the main tendencies and prospects of their development are considered. Recent works of FGUP “VIAM” in the field of creation and approbation of various-purpose low-alloy titanium alloys are reviewed.

The effect of annealing at up to 550°C on the electrical resistivity ρ and HB hardness of low-alloy alloys of the Al – Zr – Si system containing up to 0.3% Zr and 0.3% Si is studied. The Thermo-Calc software is used to analyze the phase composition of the system. The computed and experimental data are used to determine the lower and upper limits for heating of cast preforms from Al – Zr alloys (shaped castings and ingots). It is shown that heating below 400°C and above 450°C is not expedient, because it increases the duration of the annealing in the former case and lowers the hardening effect due to coarsening of the Zr-containing particles in the latter case.

Seven heats of alloy V95ochT2 are studied after a heat treatment imitating the conditions of the appearance of dark spots in the production process and anodic oxidizing (anodizing). The mechanical properties, the hardness, the structure, and the electrical conductivity of the alloy are determined. The causes and conditions of the appearance of dark spots are analyzed. The transparence of the film is shown to worsen upon formation of particles of second phase in the alloy.

A process for fabricating 5-mm-thick sheets from alloy 1565ch with recrystallized grains less than 10 μm in size is developed, which involves superplastic forming and provides elevated mechanical properties at room temperature. The parameters of superplasticity and the mechanical properties of alloy 1565ch are determined. Test forming of a dome-shape model part is performed.

Low-alloy steel 35CrMnSi (0.37% C, 1.18% Cr, 0.85% Mn, 1.24% Si) is studied after an annealing – quenching – partitioning heat treatment. The steel with an initially martensitic structure is subjected to 15-min austenitizing in the intercritical temperature range of 790 – 810°C, quenching to a temperature below M_s (240°C), 100-sec holding at this temperature for redistributing the carbon between the phases, and water cooling. The mechanical properties of the steel are determined in tensile tests and the microstructure is studied by light and scanning electron microscopy. Fracture surfaces are investigated. A mode of annealing – quenching – partitioning heat treatment is suggested for creating an optimum microstructure raising the elongation without worsening the high strength properties of the steel.

Formation of micropores near nonmetallic inclusions under fatigue fracture of a bearing steel is considered. Dependences of pore formation on the temperature of hot rolling of the steel and relations between the number of pores and the deformation temperature are presented. Recommendations are given on the deformation temperature ranges.

Magnetic domain structure is studied in single crystals of R₂Fe₁₇ (R = Tb, Dy, Ho, Er) intermetallic compounds in a wide range of temperatures (10 – 300 K) and magnetic fields (μ₀H = 0 – 0.1 T). It is shown that single crystal specimens of hexagonal magnetics with planar-type anisotropy acquire domain structures containing not only 180-degree domain boundaries but also 60- and 120-degree ones.

The phase composition and microstructure of Sm – Fe alloys obtained by vacuum induction melting of the elements are studied near the stoichiometry of Sm₂F₁₇ by the methods of scanning electron microscopy, local microanalysis and x-ray analysis. The possibility of coherent junction of all the phase components of an ingot is analyzed with the help of representation of the crystal structures of all intermetallics of the Sm – Fe system in terms of coordination polyhedrons. It is shown that long-term annealing at a high temperature (for 30 h at 1150°C) does not remove from the structure of the ingot the regions of metallic samarium formed due to the peritectic type of solidification of the Sm₂Fe₁₇ intermetallic.

The method of regression analysis is used to obtain equations describing the dependences of magnetic hysteresis properties of magnetically hard powder alloy Fe – 28% Cr – 13.4% Co – 2% Mo – 0.5% Si on regimes of thermomagnetic treatment (the temperatures of the start of the treatment and the rates of cooling in magnetic field). The determined treatment modes make it possible to obtain in an alloy with a coercive force H_c up to 40 kA/m, a residual induction B_r up to 1.2 T, and a maximum energy product (BH)_max up to 25 kJ/m³. The alloy may find application in the production of rotors of synchronous hysteresis-reluctance motors.

The magnetic and mechanical properties of two hard magnetic alloys (30Kh21K3M and 30Kh20K2M2V) of the Fe – Cr – Co system in anisotropic and isotropic conditions produced by traditional induction melting and by the method of powder metallurgy with subsequent pressure treatment of the metal are studied. The obtained regression equations for B_r, H_cB and (BH )_max describe the quantities adequately in the used range of variation of factors. The response surfaces and their sections in the phase space of the heat treatment factors are plotted. The results of the analysis of the proportion of residual induction in anisotropic and isotropic states are used to infer that the model of the mechanism of magnetization reversal of hard magnetic alloys of the class considered needs amending.

Methods for determining the weber-ampere characteristics of electrical devices, one of which is based on solution of direct problem of harmonic balance and the other on solution of inverse problem of harmonic balance by the method of full-scale-model tests, are suggested. The mathematical model of the device is constructed using the describing function and simplex optimization methods. The presented results of experimental applications of the method show its efficiency. The advantage of the method is the possibility of application for nondestructive inspection of electrical devices in the processes of their production and operation.

The evolution of defective structure in a single crystal of a Ni₃Al-base intermetallic with iron and chromium additives under the conditions of superplasticity (δ = 140%) is studied by transmission electron microscopy. The tensile deformation is performed a 1150°C. Planar flaws and recrystallized grains are detected in the fractured zone of the metal. The mechanisms of high-temperature superplasticity of alloys based on Ni₃Al intermetallic are discussed.

Transformations that occur under heating in the structure of high-manganese steel 110G13L are studied. The carbon content in the steel is shown to affect the optimum temperature of heating the high-manganese castings for quenching. An empirical formula for determining the total duration of heating and holding of this type of castings for quenching is obtained.

The effect of shot peening treatment on high-cycle fatigue of high-strength cast iron with globular graphite is studied. The fatigue curves are plotted, the microhardness and the surface roughness are measured. An analysis of fracture surfaces is performed, and the thickness of the hardened layer is determined. The shot peening is shown to affect favorably the fatigue resistance of the iron but to worsen the condition of the surface.

Amethod for simulating the hysteretic properties and the process of magnetization reversal of uniaxial highly anisotropic ferromagnets is developed with allowance for the presence of magnetostatic interaction between microvolumes of the material. It is based on the phenomenological approach to an elementary act of the process of magnetization reversal of these materials. Computer simulation is used to explain and illustrate the phenomenon of “thermal magnetization,” the formation of “channels of reversal magnetization,” the interrelation between the degree of crystal texture and the spin reorientation transfer, the coarsening of the domain structure in rapidly hardened powders, and the behavior of permanent magnets in a magnetic system in contact with a magnetically soft material.