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Nanostructured pseudoalloys of immiscible Cu, Cr and W metals were prepared by combined use of high-energy ball milling (HEBM) and spark plasma sintering (SPS). Mechanical alloying in an Activator-2S planetary ball mill for 150 min provides a uniform distribution of refractory Cr and W particles in a moldable Cu matrix on a submicron and nanoscale level. Activated W-Cu-Cr powders were SPS-consolidated at 800[?]1000degC and 50 MPa for 10 min. The effect of preparation conditions on the microstructure, crystal structure, and properties (density, hardness, electric resistivity) of synthesized nanostructured W-Cu-Cr pseudoalloys was studied. The consolidated W-Cu-Cr composites showed a hardness of up to 9.5 GPa and an electric conductivity of 27-28% IACS, which makes them promising for use as an interrupter contact material.

In this work, we examined several modifications of solution combustion synthesis (SCS) method to produce new nanoscale non-oxide phases (nitrides, intermetallics, and alloys). In particularly two approaches were outlined: (i) so-called, catalytic SCS, where existence of one metal promotes reduction during combustion; (ii) synthesis by using media, which contains both reactive solution and solid metals, i.e. combination of solution and heterogeneous combustion.

Production of single-phase carbide high entropy ceramic (Hf0.2Ta0.2Ti0.2Nb0.2Mo0.2 or Zr0.2,)C by self-propagating high-temperature synthesis (SHS) from a mechanically activated (MA) reaction mixtures and mechanical synthesized (MS) materials is discussed. The influence of mechanical treatment time at ball mill, on the formation of the phase of a high-entropy material is investigated. Spark plasma sintering and their structure, phase composition, obtained bulk samples and mechanical properties were studied. A self-propagating high-temperature synthesis of high-entropic carbide based on refractory elements was also carried out. The microstructure and mechanical properties of high-entropy ceramics obtained by the methods of mechanical synthesis and SHS were compared.

This paper is devoted to the study of copper-based composite materials structure formation processes in the conditions of SPS. The structures of Cu-Cr, Cu-Mo, Cu-W, Cu-Cr-Mo, Cu-Cr-W, Cu-Mo-W, Cu-Cr-SiC, and Cu-Zr-CNTs two-component and three-component systems were analyzed. The possibility of the formation of non-equilibrium phases under SPS conditions is shown, the effect of chemical transformations on the structure of bulk composite materials is considered.

Time-varying loads negatively affect the properties and structure of materials. Structural failures typically occur at loads below the yield point. In this work, fatigue tests of welded joints of low-alloy steels were carried out in an asymmetric cycle at loads of 60 and 80% of the yield strength. The stress ratio was 0.8-0.9. On the basis of the results of the tests, equations linking the number of cycles to failure with test parameters were obtained. Such equations can be used for estimating the residual life of elements both under construction and in operation. It has been found that the failure is not instantaneous. Specimens of steels continue to resist variable loads for 4000 - 26000 cycles to failure, depending on steel grade and the parameters of the test. Under operating conditions, it gives an opportunity to discover the onset of failure and dispose of the defective part or to replace the entire structure. A standard technique was used to measure the microhardness on the fractured specimens. The distance between the nearest indentations was 0.2 mm. The results of the measurements were plotted in graphs of ahardness change characteristic for all steels under study. A microhardness "step" has been discovered in areas with high dislocation density, as evidenced by x-ray diffraction and transmission electron microscopy. An intermediate stage of the investigation is the development of recommendations for determining the moment of failure of welded constructions with a probability of 95%.