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

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.

The paper presents experimental data on the tribological properties of commercially pure titanium with different microstructures with and without coating. As a result of the conducted experiments, it was established that the integral value of the friction coefficient, as well as its adhesion component, are structurally sensitive parameters. It is noted that the ultrafine-grained structure, obtained as a result of intense plastic deformation, contributes to the reduction of the coefficient of friction, as well as to the increase of the load-bearing capacity of tribo-conjugation.

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 work is focused on investigation of different thermomechanical treatment (TMT) regimes influencing mechanical and electrical properties of Al-Mg-Si alloy. Three TMT regimes were chosen, which differ in the number of treatment steps. Grain size, microhardness, electrical conductivity were measured. It was revealed that dividing TMT into 2 stages favorably affects formation of mechanical and electrical properties in Al6101.

At present time there is considerable interest in extending the application area of low-alloy and rather inexpensive heat- hardenable aluminum Al-Mg-Si alloys in the automotive industry, aviation, construction and electrical engineering. In this regard, the topical problem is to enhance strength and electrical conductivity of such materials, which would subsequently reduce the weight of products made of structural and electrical Al-Mg-Si materials. Severe plastic deformation is one of the promising methods of obtaining a significant increase in properties. In this paper a new SPD method is investigated – Multi-ECAP-Conform, characterized by the fact that per one processing cycle the accumulation of true strain is provided up to е>2.5. In order to study the stress-strain state effect on the mechanical properties of the aluminum Al-Mg-Si alloy, mathematical and physical modeling with the modern software Deform-3D were applied, as long as the well-established techniques of assessment of materials mechanical characteristics after plastic processing. The obtained results demonstrate the adequacy of using mathematical and physical modeling to estimate the stress- strain state by Multi-ECAP-Conform.

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.

The research paper presents the improvement on the mechanical and service properties of the austenitic stainless 0.07% C-17% Cr-9% Ni-0.7%-Ti steel in the fully austenitic state obtained by equal-channel angular pressing (ECAP) at the temperatures of 200 °C and 400 °C. Subgrain oriented structure in the Cr-Ni-Ti steel after ECAP significantly enhances the strength characteristics of steel at satisfactory plasticity. The fatigue limit of steel after ECAP at T = 200 ° C is higher than that after ECAP at T = 400 ° C, increasing in comparison with the initial state by 2.2 and 1.7 times, respectively. It was revealed that severe plastic deformation by ECAP increases the friction coefficient of the material by the 1.1 and 1.7 times at T = 200 ° C and 400 ° C, respectively. Despite this, the wear rate after ECAP at T = 200 ° C and 400 ° C decreases by 7 and 40 times, respectively, compared to initial state.

This work presents the analysis of the stress-strained state of billets processed by such SPD processing techniques as "ECAP-Conform", "drawing with shear" and "rotary forging" with a special geometry of anvils. We analyze the influence of processing by these SPD techniques, as well as by their combination with conventional metal working methods, on the structure formation and enhancement of properties in Al and Cu-based alloys, as well as in low-carbon steel. We demonstrate the critical role of the induced non-monotonous deformation in the formation of a combination of enhanced physical and mechanical properties in the investigated metallic materials during treatment by combined and consecutive SPD techniques.

Structure and properties of low-alloyed copper-based alloys with Cr, Zr and Hf after severe plastic deformation (SPD) using techniques of high pressure torsion (HPT) and equal channel angular pressing (ECAP) have been studied. SPD significantly increases strength of the alloys by formation of ultrafine-grained structure. Cu5Zr and Cu5Hf particles suppress the grain growth in ultrafine-grained (UFG) structure more effectively than the Cr particles and provide additional hardening during aging. Moreover, it was found that the application of additional aging after SPD significantly improves service properties of the alloys (fatigue limit, wear resistance and electrical conductivity). This combination of properties results in a high durability of electrodes for resistance spot welding produced from UFG Cubased alloys.

This paper presents the results of the computer and experimental study of a promising technique of severe plastic deformation (SPD) – Multi-ECAP-Conform (M-ECAP-C) for the fabrication of long-length nanostructured billets (wire rods) with an enhanced strength and electrical conductivity from the aluminum alloy EN-AW 6101 in a single processing cycle. On the basis of the obtained results, a new rational geometry of the pressing channel for the M-ECAP-C technique has been developed. The stress-strained state, structure and mechanical properties of pilot samples of wire rods have been studied. It has been established that processing by the new technique leads produces enhanced mechanical and physical properties.