卷 60, 编号 9-10 (2019)

The effect of manganese and iron on the structure of AK12 silumin is studied by microscopic x-ray diffraction and spectrum analyses. Experimental alloys with Fe : Mn = 1 : 0, 1 : 0.5, 1 : 0.7 and 1 : 1 are investigated. Quantitative analysis of the microstructure is performed. The hub zone is studied for two models of car wheels. Recommendations for alloying AK12 silumin with manganese and iron for raising its mechanical characteristics are given.

Aluminum alloy 6061 is studied after an ultrasonic treatment conducted at different vibration amplitudes in the casting process. The alloy is subjected to a diffraction analysis with processing of the spectra by the Rietveld method using the MAUD (Materials Analysis Using Diffraction) software. The texture parameters, the rms strain, the lattice parameter, and the crystallite size are determined by the Rietveld technique. It is shown that the porosity of the alloy deceases considerably after the ultrasonic treatment, which also affects positively the texture of the alloy.

Composite materials based on aluminum alloy Al – 9% Si – 0.6% Mg are obtained by stirring ceramic particles of silicon carbide into the melt and subsequent pressure crystallization. The effect of the content of ceramic particles on the properties of the composites is studied. It is shown that the joint use of two operations, i.e., stirring-in of particles and pressure crystallization, lowers the porosity and improves the distribution of particles in the structure. The composite materials obtained possess high mechanical properties and promise successful application in the automotive and aerospace industries.

Comparative analysis of the microstructure and microhardness of austenitic-ferritic high-strength iron after heat treatments involving single-stage and double-stage quenching from the austenitic or intercritical temperature ranges and tempering is performed with the use of dilatometry, measurement of microhardness, and optical and scanning electron microscopy. The possibility of the use of two-stage austenitization for heat treatment of austenitic-ferritic cast irons for raising their properties is studied.

The structure of surface layers of titanium alloy OT4 subjected to non-vacuum electron-beam treatment with power density of the beam equal to 0.28 – 0.90 kW/cm² is analyzed. The microstructure of different zones of the material after the treatment and the crystallographic texture appearing in the surface layers as a result of the electron-beam impact are studied. The microhardness of the remelted layers and of the heat-affected zone is measured. Mathematical modeling is used to obtain the distribution of the temperatures and the heating and cooling rates over cross section of the treated material.

The effect of the structural transformations during non-vacuum electron-beam cladding of amorphous boron powder on the hydroabrasive wear resistance of the surface layers of a chromium-nickel austenitic steel is studied. It is shown that the cladding yields a coating with densely arranged borides. An x-ray method is used to show that the modified layer consists virtually fully of Fe₂ B iron borides. This structure raises the hydroabrasive strength of steel 12Kh18N9T by a factor of 1.5 – 2.

The effect of additions of niobium in an amount of from 20 to 35 wt.% on the structure and properties of two-component Ti – Nb alloys is studied in cast condition and after a homogenizing annealing. The structure of the alloys is determined by optical and scanning electron microscopy, x-ray spectrum analysis and diffraction of synchrotron radiation. The lattice parameters of the formed phases and the mechanical properties of the alloys are assessed.

Results of mathematical simulation of the distribution of the concentrations of carbon and alloying elements in the zone of interaction of dissimilar microvolumes formed by spark plasma sintering of particles of steels 12Kh18N10T and U8 at various sintering temperatures and times, results of investigations of the structure of the specimens, and results of a regression analysis of experimental data are presented. The laws of formation of transition zones are described with the use of regression analysis based on the generalized lambda-distribution and on the method of truncated least squares. The processed data make it possible to identify the effect of the sintering mode on the structure of the transition zones. The results of the diffraction studies and their statistical analysis prove the results of the statistical simulation of the chemical composition.

The effect of pre-recrystallization annealing on the evolution of the structural and phase state and the deformation and fracture behavior of ultrafine-grained titanium alloy VT16 obtained by pressing with change of the deformation axis and gradual lowering of the temperature within 1023 – 723 K is studied. It is shown that the process of pre-recrystallization annealing is accompanied by retrogression of the strained structure, which lowers the strength characteristics, and by a β → α phase transformation and redistribution of the alloying elements, which keep the strength properties at a high level.

The nature of stability of dendritic microsegregation of rhenium in single crystals of intermetallic (γ′ + γ) alloys based on γ′-Ni₃Al is determined under a high-temperature heat treatment and under creep and endurance tests. It is assumed that steady dendritic microsegregation of rhenium is a factor determining the high high-temperature strength of rhenium-containing (γ′ + γ) alloys based on γ′-Ni₃Al.

A facility for physical simulation is used to plot dependences of flow stress on the degree of deformation in the temperature range from 1000 to 1230°C at deformation rates from 0.1 sec^–1 to 50 sec^–1 for alloy KhN55MBYu-VD. The dependences obtained and the results of the determination of grain sizes are used to calculate the coefficients for models of the kinetics of dynamic recrystallization based on a Johnson–Mehl–Avrami–Kolmogorov-type equation and of growth of dynamically recrystallized grains. The simulation of the grain size variation during dynamic recrystallization has shown that the deviation of the computed data from the experimental ones does not exceed 15%.

Special features of the structure of surface layers formed on billets of commercial-purity titanium VT1-0 by cladding a powder aluminum-titanium mixture with an electron beam removed into air atmosphere are studied. X-ray phase analysis and transmission electron microscopy are used to show that the material remelted by the electron beam is Ti₃Al titanium aluminide. The hardness of the deposited layer is 540 – 610 HV. The behavior of the material is studied under the conditions of sliding friction and friction against fixed abrasive particles. The results reflect decrease in the friction factor and increase in the wear resistance of the clad material as compared to commercially pure titanium.

Bimetals produced by explosion welding of titanium alloy VT23 and steel 45KhNM through an intermediate layer of steel 08ps followed by a heat treatment consisting of quenching and tempering are studied. The three-layer composite is subjected to metallographic analysis prior to and after the heat treatment with the help of an optical microscope and a scanning electron microscope equipped with an energy dispersive analyzer. The chemical composition and the hardness of the welded materials and of various regions of the weld are determined, and the changes in these parameters after the quenching and tempering are assessed.