Bulletin PNRPU. Mechanical engineering, materials science

The study of the gradient structure arising at implantation by aluminum ions of VT1-0 alloy (technically pure titanium) in submicroscopic state was carried out. To form the submicroscopic state, a combined method of multiple uniaxial pressing (abc-pressing) followed by multi-step rolling in brook rolls at room temperature and subsequent annealing at 573 K, 1 hour was applied. Ion implantation was performed for 50 minutes at an irradiation dose of 1∙1017 ions/cm2 and a temperature of 623 K. The study was performed by transmission electron diffraction microscopy and energy dispersive X-ray spectroscopy on foils cut perpendicular to the treated surface of the sample. It has been established that the gradient structure formed by implantation consists of 5 layers: 1 - oxide layer; 2 - ion-implanted layer; 3 - layer with a destroyed grain structure; 4 - residual implantation effect layer; 5 - layer corresponding to the unimplanted state of the alloy. In each layer the phase composition, shape and location of the second phase particles have been determined, the size of a-Ti grains, the size, density of distribution and volume fractions of the separated particles have been measured, and the state of the solid solution has been analyzed. It was established that layer 1 is based on aluminum (Al2O3) and titanium (TiO, TiO2) oxides. The matrix of layer 2 is the a-Ti solid solution oversaturated with Al atoms, in layers 3-5 is the a-Ti solid solution. Implantation led to the formation of ordered phases: Ti3Al (superstructure D019) and TiAl3 (superstructure D022). The particles of Ti3Al phase in the layer 1 are present in the form of separately arranged nanograins, in layers 2 and 3 have a lamellar shape and are located inside, and in layer 4 along the grain boundaries a-Ti, in the layer 5 is absent. Particles of the TiAl3 phase in layer 1 are also present in the form of nanograins, in layers 2 and 3 they have a rounded shape and are arranged randomly, in layers 4-5 they are absent.

The two-phase (α+β)-titanium alloy VT23 in the initial state after annealing at a temperature of 750 °C was used as the object of research. The heat treatment of annealed samples included quenching from temperatures of 800 and 860 °C in order to regulate the stability of the β-phase. In order to increase the strength properties, an additional aging of a part of the samples was carried out at a temperature of 500 °C. X-ray diffraction analysis, optical and electron microscopy (EBSD analysis) were used to study the structure and quantitative phase composition of the alloy after various heat treatment modes, and the features of phase transformations during quenching and subsequent aging were revealed. The results of mechanical tests at room temperature of samples processed according to various modes for uniaxial tension and impact bending are presented. When testing discontinuous samples hardened from a temperature of 860 ° C, the value of the trigger stress necessary for the beginning of the development of the martensitic transformation βm→α, initiated by tensile stresses, was determined. The role of β-phase stability in the development of phase and microstructural transformations during aging is determined. The morphology of the fracture surface of hardened and aged samples after impact bending tests was studied by the method of electronic fractography. The results of mechanical tests showed that an increase in the quenching temperature from 800 to 860 °C leads to an increase in the characteristics of strength and impact strength. The subsequent aging of samples hardened from a temperature of 800 ° C and, especially, from 860 ° C leads to the release of particulate of the α-phase in the β-matrix, which causes a significant with a decrease in the values of elongation and impact strength.

The phase composition and structure of an alloy based on Ni-Al-Co in three states have been studied by transmission diffraction and scanning electron microscopy methods: 1) after directional crystallization (DC) - initial state; 2) DC + deformation at 1200°C to 70% compression and 3) DC + deformation at 1200°C to 20 % + annealing at 1280 °C for 1 hour + annealing at 950 °C for 24 hours. It was found that the main phases in all states are g- and g¢- phases. The γ-phase is a nickel-based solid solution. It has an fcc lattice and short-range atomic order in the arrangement of atoms. The g¢-phase is an ordered L12 phase. As a rule, these phases form the basic structure of the alloy in almost all superalloys. In the alloy under study, they are present in the form of g¢-phase quasi-cuboids separated by layers of the-phase. The measurements carried out in this work made it possible to classify particles of the g¢-phase into two scale levels: g¢-phase of the first level (g¢I) - large rounded particles with a size of 25-35 microns; the second scale level of the g¢-phase - the g¢-phase of the second level (g¢II) - quasi-cuboid particles ranging in size from 0.25 to 0.6 μm, located in a two-phase mixture g + g¢II, which surrounds large particles g¢I. Along with the main phases, the b-phase (ordered with B2 superstructure) and the e-phase (ordered with D024 superstructure) have been found. The effect of deformation and annealing on the volume fraction of phases, as well as on the size and shape of the quasi-cuboids g¢-phase, has been studied. It was found that the effect of deformation on the structure is different from the effect of deformation and annealing, namely, deformation and annealing cause a greater change in the morphology of the g¢-phase quasi-cuboids than deformation without annealing.

A study of the process of granulation of coal particles in a planetary granulator has been carried out. The aim of the work is to determine the possibility of granulation of crushed coal, to study the effect of granulation parameters (particle size distribution, the proportion of liquid binder, planetary and relative rotation speed) on the example of coal on the efficiency of obtaining granules, to determine the stages of granulation. Sieve analysis was used to determine the particle size distribution. The surface of the agglomerates and granules was studied using optical microscopy. It has been established that there are two different ways to obtain coal granules. In the first method, coal particles, crushed to the required granule size, are used as a starting material. The particles are ground in a planetary granulator without adding liquid. The resulting granules are in the form of fragments with rounded edges and tops, as well as smooth compacted edges, the strength of the granules is equal to the strength of the initial material, the surface is not subject to destruction from friction, dusting, since it is compacted. In the second method, particles with a fraction of less than 1.25 microns are used, water is added as a binder, and the process of rolling with the formation of granules occurs. During granulation, the formation of plates on the end walls of the drum was found, consisting of dust obtained as a result of grinding large particles. Measurement of the particle size under an optical microscope showed that the maximum particle size in the composition of the plates is 1.25 microns. The study of the particle size distribution of the plate from the end surface of the drum is a new way to determine the required particle size of the starting material for granulation by rolling .

The article presents the results of the market research of applied simulation programs from the point of view of the possibility and expediency of using the latter in the development or optimization of technological processes at domestic machine-building enterprises. The features of technological processes of mechanical engineering and aircraft construction at domestic enterprises are analyzed. The main stages of the development of simulation modeling programs and the features of modifying application programs at these stages are studied. The features of the production of metal-intensive products and semi-finished products are studied from the point of view of the feasibility of simulation modeling of these processes. The expediency of conducting simulation modeling of machine-building industries is determined, which provides adequate analysis results at minimal cost compared to other modeling methods. The main criteria for selecting a specific simulation software are defined. It is noted that the most important advantage of software systems is not the ability to visualize the results of mathematical modeling of technological processes, but the ability of the program to apply various available analysis mechanisms, such as sensitivity analysis, optimization of the production environment, the use of the Monte Carlo method, the possibility of scenario analysis. It is determined that an extensive set of analytical tools of software environments (bottleneck analysis, statistical data and graphs) helps to evaluate various production scenarios. Various simulation modeling programs are considered, representing both domestic and foreign developments that are advisable to use in the design and optimization of mechanical engineering processes. It is established that all the analyzed programs provide production planning, design of production facilities and productivity planning, process improvement, analysis of weak points, optimization of the production cycle, optimization of resources: personnel and equipment, provide planning of stocks (in particular, work-in-progress and raw materials). In this article, the ranges of application of these programs are defined. The price range of simulation software environments suitable for modeling production processes of mechanical engineering has been established.