Bulletin PNRPU. Mechanical engineering, materials science

The influence of different regimes of thermal cycling on the structure, microhardness and magnetic properties of the ternary Heusler alloy based on Ni-Mn-In was studied. The microstructure of Ni47Mn42In11 alloy was investigated in the annealed condition and after thermal cycling by optical metallography and scanning electron microscopy. Magnetic and structural transition (martensite) transformations were observed in the alloy during cooling. Martensite transformation was accompanied by the change in the crystal lattice and microstructure. The structure of the investigated alloy after annealing was biphasic consisting of a high-temperature L 21 phase and martensite crystals. After annealing the alloy has a polycrystalline state with a predominantly smooth boundaries of initial coarse grains. Thermocyclic treatment was performed after annealing in different regimes. The heating temperature was varied in the single-phase region of existence of L 21 phase (from 363 to 473 K), cooling temperature was varied in low temperatures (233-77 K) and the number of heating-cooling cycles was varied (up to 30). As a result of structural studies it was found that after thermal cycling there are changes in the structure, in some cases the shape of the grain boundaries were changed, distorted jagged grain boundaries were appeared. It was shown that after thermal cycling with increasing number of cycles of heating and cooling rate microhardness was increased as compared with the value of microhardness in the annealed condition. Temperature dependences of the amplitude magnetic susceptibility on cooling and heating were measured after annealing and after subsequent thermal cycling. It was shown that multiple thermocyclic treatment does not cause a significant change in the magnetic susceptibility of the studied alloy.

During electric discharge machining of the workpiece material is subjected to electrical pulses. Under the action of high temperatures, the phase transition material being processed from a solid to a vapor. metal vapors in contact with the process fluid that fills the space between electrodes, harden and form EDM sludge. On the basis of literary analysis shows that result of the turbulent motion of sludge particles collide, resulting in the occurrence of dents and cracks on their surface. The collision of the spherical particles are larger and smaller particles occurs inclusions structure. Furthermore, the presence of the viscous working fluid leads to the formation of conglomerates of particles EDM slurry. Influence of EDM mode on the formation of conglomerates of the sludge particles has not been studied fully. Objective - metallographic analysis of the morphology of erosion products in the processing of titanium alloy VT1L. It is found that the EDM sludge consists not only of the processed alloy particles, but also from the electrode particles. The value of output level determines the amount of electrical discharge of sludge particles. It is shown that the minimum power the unit particle size is minimal. It noted the intense conglomeration of small particles difficult to remove the products of erosion from the treatment zone. Measurements showed that the conglomerates obtained in the lower power modes (finishing modes), is larger and consists of a large number of small particles than the high-power mode. It is found that the particles conglomerates composed of the electrode-tool and electrode-piece. It is shown that with increasing pulse energy, the particles do not conglomerate EDM sludge, the sludge is individual elements with a mean size of 14 microns.

Microstructural peculiarities of steel and aluminum layers of the layered composite 09G2S-AMc obtained by rolling at 600 °C are studied. Objects of the research are 11-layered composite which consists of low-carbon steel 09G2S and aluminum alloy AMc, and the materials in the initial state. Microstructural observations of composite and its components in the initial state were carried out with application of scanning (TESCAN VEGA II XMU) and transmission electron microscopy (JEM 200ЕХ). Reconstruction of the microstructure with the determination of the grain crystallographic orientation and the average grain size of the composite and its components is realized by the electron backscatter diffraction method (EBSD). The structure evolution of the steel and aluminum layers of the composite during the rolling are determined by results of TEM micrographs analysis. The evaluation of dynamic fracture resistance of composite was conducted according to the results of impact tests at temperatures: 20, -40 and -196 °C using instrumented pendulum impact test machine Tinius Olsen IT542. The values of impact strength, dynamic fracture resistance and energy of crack initiation and propagation in layered composite having various orientations of layers with respect to the notch line were estimated. The retention of high dynamic fracture resistance of laminated composite 09G2S-AMс with the orientation of the crack front across the planes of connection layers is connected with the introduction of the ductile layer of aluminum alloy AMc, the grain refinement of the steel layers and the creation of interlayer bonder in the process of obtaining composite, which contributed the deviation of the crack growth front along the interlayer bonder.

In the process of the metal cutting inevitably appear forced and auto-oscillations in the system "machine - fixture - tool - detail". These vibrations worsen quality of the processed surface and increase the wear of instrument. Particularly relevant issue is designated for machine tools with CNC, where slides or tables moved irregularly by using indexing mechanism and the cutting speed can be continuously varied in continuous processing of parts. In this connection, you need to ensure the monitoring of irregular movements and the control of a technical condition of automatic control systems. This article proposes a method of solving this problem on the example of inspection of a technical condition of automatic control systems of rotation frequency, which was implemented earlier with reference to automatic control systems of diesel internal combustion engines. The joint movement of any object of regulation and the regulator it is possible to present systems of the equations in the form. Nature of transition processes when using electronic, electromechanical and electrohydraulic systems of regulation can be described dependence of amplitude values of angular acceleration on time of delay of the managing director of a signal. Quality of transition processes is offered to be estimated in size of throwing of angular acceleration. The theoretical provisions provided in article prove influence of technical condition of the regulator of frequency of rotation on nature of temporary dependence of angular acceleration at change of external loading or at change of frequency of rotation of a shaft of the drive. Thus, amplitude values of angular acceleration contain reliable information about technical condition of system of automatic control in the fading oscillatory process. The offered principles of control of parameters of systems of regulation can be applied also to electric drives of the metal-cutting equipment. For an assessment of unevenness of rotation and control of technical condition of systems of automatic control it is offered to use the program and measuring complex developed at the Siberian State Transport University.This complex allows to fix parameters of transition processes in graphic and in a tabular style, to provide a conclusion to the screen of the personal computer parameter size in a concrete point of the schedule, and also with high precision to estimate characteristics of instability of the established rotation frequency. the established rotation frequency. Change of technical condition of systems of automatic control is in use estimated on a deviation of size of amplitude values of angular acceleration from reference, measured at a working order of system.

Budker Institute of Nuclear Physics, Novosibirsk, Russia, have successfully used the electron beam welding for manufacturing of vacuum chambers for a long time. The electron beam welding facility has the moving system that helps to weld seams up to 2 meters long (by using several independent launches). The electron gun has developed in the institute, the acceleration voltage is 60 kV, and the power of beam is up to 60 kW. Currently Budker Institute manufactures the dipole vacuum chambers for HEBT, FAIR (Germany). There are two types of dipole vacuum chambers for this project: or bended chambers or branching chambers. The bended vacuum chambers consist of two longitudinally EBW U-shaped stainless steel 316 LN profiles different length with the wall thickness 4 mm. After welding, the chamber bends to the required angle. The branching chamber includes three parts: two small direct parts for beam evacuation, which welded of two U-shaped stainless steel 316 LN too, and one branching segment with variable aperture area, with the wall thickness 6 mm. Three parts have welded with each other with using TIG welding. After that, there are flanges and fastening elements have been welded to the chambers. To eliminate the virtual leak, the welds will have the full penetration. The electron beam welding facility is being updated so that the maximum seam of 2 meters would be achieved with one single launch. At present time, vacuum tests were carried out for vacuum chamber prototypes in Budker Institute of Nuclear Physics and FAIR.

The analysis of scientific references on intermediate transformation is presented in article. Material of various periods of research of bainite transformation in the different countries is generalized. The main distinctions between the lower and top bainite are revealed, and also advantages of one morpho- logy of a bainite over another are shown. Some types of bainite structure at various methods of research of structure are illustrated. The terminological analysis of use of the term "carbide-free bainite" is carried out. Use of various names of structure which turns out as a result of intermediate transformation without formation of carbides is revealed. In various references what bainite is confirmed can be carbide-free bainite. The aspiration to receive carbide-free bainite is deals with the raised complex of mechanical properties at this structure. Realization of such structure is possible in strict observance of technology of heat treatment. Therefore in article ways of heat treatment are analysed. It is revealed from scientific literature that carbide-free bainite it is possible to receive as a result of continuous cooling and isothermal holding at addition in steel of elements which allow to exclude carbide forming. Distinguish silicon and aluminum from such elements. The last decade the perspective direction is Quenching & Partitioning treatment from which formation of bainite and martensite structure with various maintenance of this or that component results. In article carrying out the modes of heat treatment on the traditional furnace equipment is also considered. It became known that some scientists research the structure received when cooling from an intercritical interval.

Rapid prototyping technologies are widely used in the foundry industry in the manufacture of precision electrodes-tools for EDM. The accuracy of manufacturing of prototypes for rapid prototyping technology depends on a number of process parameters, such as, model focus on building a working plane, the thickness of the layers, construction material, exposure modes, post-processing. Currently used as an epoxy material and acrylic resin material having a shrinkage and the presence of residual stresses in layer wise solidification process and post processing, which leads to loss of dimensional precision. The paper presents an analysis of the dimensional accuracy of the samples for the manufacture of photopolymer mask stereolithography material technology based on acrylic SI500, depending of type of model orientation. To evaluate the accuracy, simulated samples of rectangular form, the experimentally chosen mode of construction to install Envisiontec Perfactory Xede and tilt angles of the model to the working surface of the construction. Measurements of the samples after the construction were carried out in three sections between parallel planes. A result of research found that the orientation of the model under the minimum angles in 5º, 10º, 15º affects the dimensional accuracy of the prototype. The maximum size of the deviation of the sample sections between by planes are observed at the orientation of the model at an angle of 5 and 15º and make 0.26 mm and 0.14 mm, respectively. The most accurate sample obtained by the model orientation at an angle of 10º, the maximum deviation of the size which is 0.09 mm. As a second indicator of the accuracy is defined non planarity samples planes. Minimum surface non planarity is retained when the surface orientation of the sample in building 10º and makes 0,02 mm.