Phase transformations in the system Cu-Zn-Al under conditions far from equilibrium

It is shown that the alloy Cu-Zn-Al is a multiphase material. Under equilibrium conditions this alloy can form an α-phase (FCC crystalline lattice) and a β-phase (simple cubic crystalline lattice) based on copper. The possibility of formation of a γ-phase due to a three-component alloy composition is revealed. It is established that different chemical composition of the copper-based solid solution (alloys with zinc or alloys with aluminum), different concentration of the second element in a solid solution leads to the fact that within the same type of the crystalline lattice there is a certain amount of α- and γ-phases, differing in the parameter value of the crystalline lattice. The possibility of formation of powder alloys with an x-ray amorphous and a nanocrystalline structure using the plasma chemical synthesis methods is demonstrated. A wide variety of binary phases, each with different concentrations of zinc and aluminum in a solid copper-based solution is revealed. These results indicate that plasma-chemical synthesis of metal alloy powders is accompanied by separation of elements. Powders of the ternary composition are not detected

Surface modification of Ti alloy by electro-explosive alloying and electron-beam treatment

By methods of modern physical metallurgy the analysis of structure phase states of titanium alloy VT6 is carried out after electric explosion alloying with boron carbide and subsequent irradiation by pulsed electron beam. The formation of an electro-explosive alloying zone of a thickness up to 50 µm, having a gradient structure, characterized by decrease in the concentration of carbon and boron with increasing distance to the treatable surface has been revealed. Subsequent electron-beam treatment of alloying zone leads to smoothing of the alloying area surface and is accompanied by the multilayer structure formation at the depth of 30 µm with alternating layers with different alloying degrees having the structure of submicro - and nanoscale level

Fatigue life of silumin treated with a high-intensity pulsed electron beam

The regularities of the formation of the structure of silumin irradiated with a high-intensity electron beam in different modes are revealed using optical and scanning electron microscopy. The optimum irradiation mode that allows one to increase the fatigue life of this material by a factor of up to 3.5 is determined. The probable causes of the observed effect are investigated

Fatigue variation of surface properties of silumin subjected to electron-beam treatment

The analysis of structure-phase states modification of silumin subjected to electron beam treatment with the following fatigue loading up to the failure is carried out by methods of transmission electron diffraction microscopy. The tribology and strength properties of silumin surface after electron beam treatment and fatigue tests are studied and hardness decrease, wear coefficient and friction coefficient increase with the growth of cycles number are revealed. The possible reasons of the tribology and strength properties of silumin surface layers decrease are discussed

Formation structural phase gradients in rail steel during long-term operation

The paper presents results of the structural and phase analysis of the surface layer composition in the type R65 rail steel in its original state and after long-term operation. It is shown that long-term operation of rail steel is accompanied by its structural and phase modification at a depth of not less than 2 mm. The structural elements are detected that can be stress concentrators

Formation of a microcomposite structure in the surface layer of yttrium-doped titanium

Surface layers containing oxides and carbides of titanium and yttrium are prepared by the electroexplosive doping of titanium with yttrium. The subsequent electron-beam irradiation leads to dispersion of the structure to a nano- and submicron state. The formation of two types of eutectics is revealed using scanning electron microscopy. The eutectics enriched in titanium and yttrium have a globular and plate-like shape, respectively. The formation of a modified surface layer (enriched in yttrium, carbides and oxides of titanium and yttrium) leads to a threefold increase in the microhardness of the titanium, a more than twofold decrease in the friction coefficient of the doped layer, and a more than 2.8-fold decrease in the wear rate

Fractography of the fatigue fracture surface of silumin irradiated by high-intensity pulsed electron beam

The surface modification of the eutectic silumin with high-intensity pulsed electron beam has been carried out. Multi-cycle fatigue tests were performed and irradiation mode made possible the increase in the silumin fatigue life more than 3.5 times was determined. Studies of the structure of the surface irradiation and surface fatigue fracture of silumin in the initial (unirradiated) state and after modification with intense pulsed electron beam were carried out by methods of scanning electron microscopy. It has been shown, that in mode of partial melting of the irradiation surface the modification process of silicon plates is accompanied by the formation of numerous large micropores along the boundary plate/matrix and microcracks located in the silicon plates. A multi-modal structure (grain size within 30-50 μm with silicon particles up to 10 μm located on the boundaries) is formed in stable melting mode, as well as subgrain structure in the form of crystallization cells from 100 to 250 μm in size). Formation of a multi-modal, multi-phase, submicro- and nanosize structure assisting to a significant increase in the critical length of the crack, the safety coefficient and decrease in step of cracks for loading cycle was the main cause for the increase in silumin fatigue life

Electrospark doping of steel with tungsten

The paper is devoted to the numerical modeling of thermal processes and the analysis of the structure and properties of the surface layer of carbon steel subjected to electrospark doping with tungsten. The problem of finding the temperature field in the system film (tungsten) / substrate (iron) is reduced to the solution of the heat conductivity equation. A one-dimensional case of heating and cooling of a plate with the thickness d has been considered. Calculations of temperature fields formed in the system film / substrate synthesized using methods of electrospark doping have been carried out as a part of one-dimensional approximation. Calculations have been performed to select the mode of the subsequent treatment of the system film / substrate with a high-intensity pulsed electron beam. Authors revealed the conditions of irradiation allowing implementing processes of steel doping with tungsten. A thermodynamic analysis of phase transformations taking place during doping of iron with tungsten in equilibrium conditions has been performed. The studies have been carried out on the surface layer of the substrate modified using the method of electrospark doping. The results showed the formation in the surface layer of a structure with a highly developed relief and increased strength properties

Детерминанты налогового стимулирования инвестиционной активности предприятий

The article is devoted to the problematic issues of tax incentives for Russian companies. The main prerequisite of the research is that the domestic practice of tax incentives does not meet the interests of the state, since it is in clear contradiction with the declared principles of economic development. The provided tax privileges should promote the investment activity of business. However, tax incentives are often offered to those enterprises that are not able to use them effectively. Justification of tax benefits requires identifying enterprise’s investment activity factors, the level of which is largely determined by the corporate life cycle stage and industry specificity. Hypotheses about the importance of corporate age and economic activity, formulated for the purposes of this study, have been empirically confirmed. It was proved that the investment activity of Russian enterprises demonstrated different dynamics in the conditions of the economic crisis. In the manufacturing industry, in particular, most enterprises increased the volume of fixed assets, while in the spheres of petroleum products, dairy products, chemical products, communications on the basis of wire technologies, there was a decline in investment activity. The change in investment activity in the period under study was due to various factors for both enterprises of different industries and enterprises of the same industry characterized by different corporate ages. The results obtained let us conclude that a unified approach to tax incentives for enterprises’ investment activity cannot be justified. In the opinion of the authors, “targeted” tools of tax incentives are more efficient.Highlights 1. Tax incentives should meet the interests of the state, contributing to the development of the economy. However, in Russia it is increasingly reduced to tax benefits, which increase in volume, but do not bring the desired effect, including the fact that they do not contribute to the growth of investment activity of enterprises2. It was revealed that the investment activity of the enterprise depends to a significant extent on the stage of the life cycle and industry specificity, which, in the opinion of the authors, should be considered as the determinants of tax incentives. Accordingly, the authors offer the hypotheses about the importance of the corporate age and the sphere of financial and economic activity in shaping the factors of Russian enterprise investment activity3. Investment activity models for young, adult and old manufacturing enterprises, as well as companies for the manufacture of coke and refined petroleum products, dairy products, chemicals and chemical products, and communications based on wire technologies have been constructed. It is shown that these models have independent significance, and the factors of investment activity really depend on the corporate age and industry specificity4. Thus, it is argued that the system of tax incentives in Russia requires development: we should abandon unsystematic tax incentives in favor of target instruments that take into account the financial characteristics of the taxpayer more flexiblyFor citation Ivanov V. V., Lvova N. A., Pokrovskaia N. V. Naumenkova S. V. Determinants of tax incentives for investment activity of enterprises. Journal of Tax Reform, 2018, vol. 4, no. 2, pp. 125–141. DOI: 10.15826/jtr.2018.4.2.048Article info Received June 9, 2018; accepted July 22, 2018Статья посвящена проблемным вопросам налогового стимулирования российских предприятий. Главная предпосылка исследования заключается в том, что отечественная практика налогового стимулирования не отвечает интересам государства, поскольку вступает в явное противоречие с декларируемыми принципам экономического развития. Так, предоставляемые налоговые льготы должны способствовать инвестиционной активности бизнеса. Однако, налоговые льготы зачастую представляются тем предприятиям, которые не способны использовать их эффективным образом. Обоснование системы налоговых льгот требует выявления факторов инвестиционной активности предприятий, уровень которой во многом определяется стадией жизненного цикла и отраслевой спецификой. Гипотезы о значимости корпоративного возраста и сферы экономической деятельности, сформулированные в целях настоящего исследования, получили эмпирическое подтверждение. Было доказано, в условиях экономического кризиса инвестиционная активность российских предприятий демонстрировала разную динамику. В частности, в обрабатывающей промышленности большинство предприятий наращивало объем основных средств, тогда как в сферах производства кокса и нефтепродуктов, молочной продукции, химических веществ и химических продуктов, связи на базе проводных технологий наблюдался спад инвестиционной активности. В то же время изменение инвестиционной активности в исследуемом периоде объяснялось разными факторами как для предприятий разных отраслей, так и предприятий одной отрасли, характеризующихся разным корпоративным возрастом. Полученные результаты позволили сделать вывод о том, что унифицированный подход к налоговому стимулированию инвестиционной активности предприятий нельзя признать оправданным. По мнению авторов, более эффективны «целевые» инструменты налогового стимулирования. Рекомендации в этом отношении могут представлять интерес для отечественного законодателя и тех лиц, в сферу интересов которых входит мониторинг инвестиционного климата в Российской Федерации.Основные положения1. Налоговое стимулирование должно отвечать интересам государства, способствуя развитию экономики. Однако в России оно все больше сводится к налоговым льготам, которые увеличиваются в объемах, но не приносят желаемого эффекта, в том числе не способствуют росту инвестиционной активности предприятий2. Выявлено, что инвестиционная активность предприятия в существенной степени зависит от стадии жизненного цикла и отраслевой специфики, которые, по мнению авторов, должны рассматриваться как детерминанты налогового стимулирования. Соответственно, сформулированы гипотезы о значимости корпоративного возраста и сферы финансово-хозяйственной деятельности в формировании факторов инвестиционной активности российских предприятий3. Построены модели инвестиционной активности для молодых, зрелых и старых предприятий обрабатывающей промышленности, а также компаний по производству кокса и нефтепродуктов, молочной продукции, химических веществ и химических продуктов, связи на базе проводных технологий. Показано, что данные модели имеют самостоятельную значимость, а факторы инвестиционной активности действительно зависят от корпоративного возраста и отраслевой специфики4. Таким образом, аргументировано, что система налогового стимулирования в России требует развития: следует отказаться от бессистемных налоговых льгот в пользу целевых инструментов, более гибко учитывающих финансовые особенности налогоплательщикаДля цитированияИванов В. В. Детерминанты налогового стимулирования инвестиционной активности предприятий / В. В. Иванов, Н. А. Львова, Н. В. Покровская, С. В. Науменкова // Journal of Tax Reform. — 2018. — Т. 4, № 2. — С. 125–141. — DOI: 10.15826/jtr.2018.4.2.048Информация о статьеДата поступления 9 июня 2018 г.; дата принятия к печати 22 июля 2018 г

Optical properties and Zeeman spectroscopy of niobium in silicon carbide

The optical signature of niobium in the low-temperature photoluminescence spectra of three common polytypes of SiC (4H, 6H, and 15R) is observed and confirms the previously suggested concept that Nb occupies preferably the Si-C divacancy with both Si and C at hexagonal sites. Using this concept we propose a model considering a Nb-bound exciton, the recombination of which is responsible for the observed luminescence. The exciton energy is estimated using first-principles calculation and the result is in very good agreement with the experimentally observed photon energy in 4H SiC at low temperature. The appearance of six Nb-related lines in the spectra of the hexagonal 4H and 6H polytypes at higher temperatures is tentatively explained on the grounds of the proposed model and the concept that the Nb center can exist in both C1h and C3v symmetries. The Zeeman splitting of the photoluminescence lines is also recorded in two different experimental geometries and the results are compared with theory based on phenomenological Hamiltonians. Our results show that Nb occupying the divacancy at the hexagonal site in the studied SiC polytypes behaves like a deep acceptor