International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The features of localization of severe plastic deformation in a steel matrix near non-metallic inclusions are studied. In the steel matrix, near inclusions and at the inclusion-matrix interphase boundaries, the nature of the stressed and deformed states changes, the strain increment is determined by the rotation angle of the inclusion during its movement in the plastic region. Processes of local structural transformations near non-metallic inclusions in steels exposing to intensive plastic deformation were investigated. The influence of non-metallic inclusions on the local refinement of the steel microstructure is an important effect during severe plastic deformation, which makes it possible to obtain additional nanostructural strengthening near the inclusions during the general refinement of grains to a submicrocrystalline state. It was shown the influence of non-metallic inclusions on mechanical properties of these steels.

This paper presents experimental data on the tribological properties of the Mg-1%Ca magnesium alloy with different microstructures (coarse-grained microstructure in the initial state, and ultrafine-grained and nanocrystaline microstructures after severe plastic deformation via two processes – equal-channel angular pressing and high pressure torsion) in contact with an indenter made of the Fe-18W-4Cr- 0.8C steel without any coating and with applied hydroxyapatite, which is the main mineral component of bones. An indenter with hydroxyapatite on the surface was used as a bone simulator. As a result of the experiments, it was found that the shear strength of adhesive bonds and the adhesive component of the friction coefficient are structurally sensitive parameters. For all the samples in the considered contact pairs, when using a bone tissue simulator the strength of adhesive bonds was lower than that when using a steel indenter. It is noted that ultrafine-grained and nanocrystalline structures produced as a result of severe plastic deformation via two processes, equal-channel angular pressing and high pressure torsion, contribute to a decrease in the shear strength of adhesive bonds and the adhesive component of the friction coefficient due to strengthening resulting from grain size reduction from originally 100 μm to 1.4–4 μm on average in the investigated Mg-Ca magnesium alloy.

On the basis of review of last developed combined metal forming processes the new concepts of severe plastic deformation combined processes aimed at further improving the deformation performance are proposed. The presence in all three proposed variants of the ECAP scheme will allow deforming without significantly changing the initial dimensions of the workpiece.

The paper presents the results of studies of tribological properties of the contact of the tool steel composition Fe-18W-4Cr-1,2V with the magnesium alloy AZ91D strengthened by submicron powder filling out of SiC and severe plastic deformation (SPD), namely equalchannel angular pressing (ECAP). It is stated that introduction of SiC powder filling to the magnesium alloy the friction coefficient on the moving frictional contact increases, the wear rate reduces. These tribotecnical characteristics are influenced by the size and volume of the particles of powder filling, normal loading force and slip rate. SPD of the initial material results in reduction of the adhesion constituent of the friction coefficient.

The development of new technological methods of SPD for the production of mass production with improved properties due to the deep grinding of the original structure is an important task. The purpose of this work was to study the active bending to grind the structure and create promising, for operational use, gradient structural states in long rods of copper grade M1. Active bending was performed using an extruder according to the “Conform” scheme. The results of the analysis stress-strain state is using computer simulation and structures using optical microscopy. It is established that the active bending method provides over four processing cycles high strain accumulation (e = 3-4) and formation subgrained- structure UFG type.

In this paper, we present the results of the tribological studies of commercially pure copper (99.9% Cu) and a low-alloyed chromium bronze (Cu-0.5%Cr), contacting a graphite-containing material. The samples under study were produced with two types of microstructures: a coarse-grained (CG) one, having an average grain size of 100-130 μm after annealing, and a submicrocrystalline (SMC) one, having an average grain size of 0.30-0.50 μm after multi-cycle severe plastic deformation (SPD) processing via equal-channel anglar pressing (ECAP) combined with Conform. It is shown that for the samples produced by ECAP-Conform, having an SMC structure, the friction coefficients are 12 – 20% lower than for the as-annealed samples, having a CG structure.

Paper presents an overall analytical review of recent achievements in the field of development and improvement of technologies for producing structural materials with ultrafine-grained structure by severe plastic deformation. Main modern methods of obtaining ultrafine-grained structure by severe plastic deformation are described. Special attention to combined process “helical rolling – pressing” is devoted.

Paper presents an overall analytical review of recent achievements in the field of development and improvement of technologies for producing structural materials with ultrafine-grained structure by severe plastic deformation. Main modern methods of obtaining ultrafine-grained structure by severe plastic deformation are described. Special attention to combined process “helical rolling – pressing” is devoted.

ECAP was conducted using route Bc with an angle of 120° between the die channels and a stepwise decrease of temperature from the initial 425 °C to 300 °C at the final, 12th pass. The cumulative equivalent strain the ECAP billets underwent was about 7.8. The structure examination showed that ultrafine-grained structure with the grain size of 0.69 – 1 μm was formed during ECAP process. In addition, particles of the phase Mg12Nd with an average size of 0.45 μm were formed. The refinement of the microstructure resulted in an improvement of the mechanical properties of the alloy. After ECAP, the strength characteristics of the alloy increased to the levels of ultimate tensile strength of 300 and yield strength of 260 MPa to be compared to those for the initial state (220 MPa and150 MPa, respectively). At the same time, the ductility increased to 13.2 %, which compares favourably with the initial value of 10.5 %. The ECAP process does not affect the resistance to electrochemical corrosion. The rate of chemical corrosion was found to be reduced owing to the ECAP processing.

This paper presents the results of preliminary corrosion tests of samples from commercially pure titanium Grade 4 with a coarse- grained (annealed) and ultrafine-grained structure after severe plastic deformation, as well as of samples processed by microarc oxidation and with an ion-plasma coating. The effect of microstructure on the corrosion of the material under study is shown. A comparative evaluation of the corrosion rate is performed.

In order to impose an extremely large strain on the bulk metal without changing the shape, many SPD processes have been developed. This paper present the numerical study of severe plastic deformation by multi-directional shearing in order to determine the materials behaviour in the case of complex solicitations conditions and estimate the magnitude of the final strains obtained. Two hardening laws are considered for describing the material behaviuor: Swift and Ludwick law. The comparison of the numerical results with experimental values for higher levels of strain shows that the Ludwick model presents a better agreement with experimental data. The presented paper gives a method and a numerical tool to study the severe plastic deformation of the materials and to predict the level of the obtained plastic strain.

This work presented the results of tribological studies of commercially pure copper (Cu 99.9%) and low-alloyed chrome bronze Cu-1%Cr in contact with a graphitiferous plate EK-40. Samples from copper and copper alloy were prepared to obtain two kinds of grain size of microstructure. Two schemes were used for tribological studies. The first scheme was used during reciprocal movement to evaluate the friction coefficient. The second scheme was employed to evaluate the shear strength of adhesive bonds and the adhesive component of the friction coefficient.Besides, the fulfilled studies determined that the tribological properties of materials depended on the grain size of microstructure. It is shown that an ECAP–Conformed specimen with UFG exhibits 20-30% lower friction coefficients than that of annealed specimen with CG structure. The tribological test results showed that the coefficient of friction decreased, with the decreasing grain size. Therefore, were conclude the coefficient of friction of proposed materials is microstructure-sensitive.