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

The possibilities of Fe-Al intermetallic system production by vacuum sintering and impact consolidation of powder bodies, as well as the influence of the regimes of the methods used on the structure and properties of iron aluminides were studied in the article. Mixture of iron and aluminum powders were used for fabrication of iron aluminide Fe₃Al. The powder samples were compacted and vacuum sintered at temperatures of 1250, 1350, 1400 and 1450 °C, and also using hot forging at a temperature of 1050 °C and 1150 °C. It is shown, that the increase of density is observed only at a temperature of 1400 °C. At sintering temperature of 1450 °C the samples reach a density of 6,35 g/cm³, which is 94% of the theoretical value. Only the use of hot forging makes it possible to obtain nonporous samples. It is shown, that bending strength, fracture toughness and hardness increase with increase of sintering temperature, but higher values of this parameters have the samples, produced with use of hot forging.

The effect of metal phase composition in the Fe-based + (2 % glass) powdered composites on the basic mechanical and tribological properties of the composites, made by means of sintering and hot forging, have been investigated. As a basis for the metallic phase of the composite the mixtures of iron powders with additives of graphite, B₄C, BN and Cu at different ratio were used. It was shown that at sintering of metal-glass material the reaction of glass phase with oxides on the surface of iron powder particles takes place, resulting in a change of glass phase chemical composition. The results of materials mechanical properties investigations had shown that the highest strength properties and hardness have the composites with the content of the initial powder mixture of 5% Cu and 2% B₄C, while the best tribological properties have the composites with 2% B₄C, 5% Cu and 1% BN.

The structural weight reduction is the most visible effect of composite application, but it’s primarily important for aircraft or spacecraft only. In engineering branches the major effect of fiber reinforcement plastics (FRP) application is the ability to solve some fundamental technical challenge, for example: simplifying design of construction, the overall dimensions reducing of the elastic element, non-fragile, etc. In this paper the methodological approach to FRP application considered. Some examples of engineering design for vehicle load-bearing FRP element are presented.

Ordinary in the theory of machine elements a deterministic stress conditions are used. In general case there are relationships between “acceptance stress” and “working stress”. In practice the stresses are random values. Therefore the stress conditions have got probabilistic formulation.

In this paper the probabilistic formulation of stress conditions for machine elements are presented.

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.

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.

On the basis of complex metallophysical studies, surface-modified layers (electron microscopy, spectroscopy, X-ray diffraction, calorimetry, durometer analysis), we obtained new data on nanoscale composition within the surface-modified layer, on its mechanical properties, phase composition, which determines functional properties. This allows us to find ways of their purposeful formation for different operating conditions. On the basis of experimental data of X-ray analysis of the TiNiHf alloy, we calculated energy consumption, the theoretical strength. As a result of the simulation, we constructed generalized diagrams of energy intensity and theoretical strength of the ternary alloy Ti-Ni-Hf and compiled their relationship equation.

This work was carried out studies on the effect of different ways of modifying the microstructure and mechanical properties of cast ductile irons identical to the final chemical composition. For comparative studies have chosen three ways of modifying the molten iron, characterized the time interval between the introduction of additives into the melt and crystallization of iron – autoclave method, processing method in an open ladle ( "Sandwich process") and a method of in-mold melt processing ("Inmold-process").

It is found that the process mold inoculation molten iron a more effective compared to other methods studied, by reducing the time interval between entering modifier in liquid iron and the onset of crystallization. This in turn enables the production of castings of several grades of ductile iron in the total process stream without additional alloying and heat treatment.

Results of research testify in favor of the fluctuation hypothesis about straight line graphitization of cast iron during primary crystallization.

The capabilities of powder hot forging for manufacturing of Fe₃Al intermetallics and effect of forging and following thermal treatment routines on their structure and properties had been investigated. Fe₃Al intermetallic powders were produced by means of thermal synthesis at 1000°С in vacuum from a mixture of Fe and Al elemental powders. Hot forging of consolidated preforms had been carried out from 1000, 1050, 1100 and 1150°С and afterwards the hot forged preforms were subjected to supplementary sintering in vacuum at 1100÷1450°С. It is foud, that thermal synthesis of Fe + 14% Al powder mixture results in formation of Fe₃Al phase. Sintering of hot forged specimens result in increasing of strength and crack growth resistance, which values enhance with increasing of sintering temperature. Otherwise the hardness of hot forged intermetallics decreases after their sintering. The influence of modes of treatment on the structure and properties of the materials was investigated. It has been established that the strength and fracture toughness of the intermetallics obtained from milled blend after hot forging had the higher values as compared with the alloy made from the batch without its milling.