Investigation of the effect of copper addition on physical and mechanical properties of TiNi-Cu porous alloy

This work is devoted to the physical and mechanical properties of porous alloys based on TiNi alloyed with different amounts of Cu additive. We show that by doping a porous TiNi alloy with copper instead of nickel, it is possible to obtain characteristics acceptable for use in implantology and superior to those of known porous TiNi alloys. Cu addition in the range from 1 to 10 at.% is shown to optimize the properties of tested alloys. There is a decrease in the minimal martensitic transformation stress τminMs from 37 to 17 MPa when compared to initial unalloyed TiNi. Alloys with 3 and 6 at.% of Cu are found to be optimal for use in medical practice. Along with a wide temperature range of reversible deformations that cover the range of operating temperatures (273–313 K), such alloys demonstrate their martensitic transformation stress values below 28 MPs. This permits to model implantable structures of complex configuration from such materials under a certain temperature regime

Study of structural features of porous TiNi-based materials produced by SHS and sintering

Structural properties of porous TiNi-based materials produced by SHS method and sintering have been investigated. The material having different pore wall surface topography, porosity and pore size distribution was shown to be produced depending on the powder metallurgy method for porous TiNi-based alloy. All the materials having porosity of 55-70%, mean pore size 90-150 μm, as well as normal pore size distribution are most preferable. Ultimate strength and breaking point were determined to depend on porosity, pore size distribution, pore intersections and phase chemical composition of the material. Strength properties of the sintered alloy are twice as much compared to the SHS-produced ones due to homogeneity of its macrostructure, low chemical heterogeneity and TiNi3 precipitations strengthening the TiNi matrix.</jats:p

On the Issue of Nitrogen Solubility in Chromium-Nickel Grades of Steels

The article presents a comparative analysis of the solubility of nitrogen in chromium-nickel grades of steels. It is revealed that the existing theoretical calculations on the solubility of nitrogen in chromium-nickel steels can be applied only to austenitic grades of steels

A METHOD OF MODIFICATION SURFACE MOULD IN GASIFICATED CASTING TO PURPOSE INCREASE WEAR RESISTANCE

The article suggests a method for increasing the wear resistance of a casting surface by introducing a pre-prepared insert with dispersed tungsten and titanium particles. The method makes it possible to obtain an extended wear-resistant layer in a metallic casting.Работа выполнена в рамках выполнения гранта Президента РФ по договору №14.Y30.18.2874-МК

Preparation of porous TiNi-Ti alloy by diffusion sintering method and study of its composition, structure and martensitic transformations

The study demonstrates a method for controlling not only the phase composition but also the atomic composition of TiNi matrix in porous TiNi-Ti alloys developed for biomedical uses as implants. The alloys were obtained from TiNi powder which was sintered with Ti powder added at as much as 0–10 at%. The structure, phase and chemical composition of the produced TiNi-Ti alloys was investigated with respect to the amount of Ti added into the material. It is shown that in the sintered product containing 5 at% and more of Ti additive, the composition of its TiNi matrix becomes close to equiatomic (with Ti:Ni atomic ratio ~1), and the excessive Ti precipitates as secondary phases Ti2Ni and Ti3Ni4. In parallel, with increase in Ti ad- ditive from 0–10 at%, the structure of the precipitating Ti2Ni type phases changes its morphology from separate spherical or pyramidal precipitates to large dendritic formations. The direct martensitic trans- formation from austenite to martensite in all the samples was found to proceed in two stages and through the R-phase (B2→R→B19′). Thermoresistive analysis demonstrated that TiNi-Ti samples with 5 and more at% of Ti had their characteristic starting temperature of martensite transition stabilizing at ~57 °C (330 K). This implies that the sample with 5 at% of Ti additive exhibited desired martensite transition temperatures, while containing a minimum concentration of secondary-phase precipitates in its matrix which deteriorate its properties. Thus, for the 곙rst time, we show that a very simple preparation approach based on sintering powders of TiNi and Ti is capable of producing porous TiNi-Ti alloys with properties optimized for fabricating bone implants

Experimental study of direct photon emission in K- --> pi- pi0 gamma decay using ISTRA+ detector

The branching ratio in the charged-pion kinetic energy region of 55 to 90 MeV for the direct photon emission in the K- --> pi- pi0 gamma decay has been measured using in-flight decays detected with the ISTRA+ setup operating in the 25 GeV/c negative secondary beam of the U-70 PS. The value Br(DE)=[0.37+-0.39(stat)+-0.10(syst)]*10^(-5) obtained from the analysis of 930 completely reconstructed events is consistent with the average value of two stopped-kaon experiments, but it differs by 2.5 standard deviations from the average value of three in-flight-kaon experiments. The result is also compared with recent theoretical predictions.Comment: 13 pages, 8 figure

HARDWARE AND SOFTWARE COMPLEX FOR EVALUATING THE SURFACE ROUGHNESS OF SUBSTRATES

The necessity of developing a software and hardware complex, which makes it possible to evaluate the surface roughness of ceramic substrates, is described. These substrates will be used in experiments to study the wettability of refractory carbides / oxides and iron-carbon melts

ENGAGING NUMERICAL MODELING TO ANALYZE METALLURGICAL AND CASTING PROCESSES

This theses present the numerical modeling of direct current electroslag remelting process and hardening dispersed carbides injection in centrifugal casting process. The computer soft-ware for modeling this processes has been described

ИССЛЕДОВАНИЕ ПРОЦЕССА ГИДРОГЕНИЗАЦИИ ОДНОСЛОЙНОГО И ДВУХСЛОЙНОГО ПИРОЛИЗОВАННОГО ПОЛИАКРИЛОНИТРИЛА

The article reports a theoretical quantum chemical study of the adsorption mechanisms in atomic and molecular hydrogen on the surface of an advanced polymeric material – pyrolized polyacrylonitrile (PPAN). Three variants of atomic hydrogen orientation and five variants of molecular hydrogen orientation over one− and two−layer PPAN surface have been considered. The variants differed in the positions of nitrogen atoms in the close vicinity of a selected adsorption center in the polymer. Potential adsorption energy profiles of atomic hydrogen and hydrogen molecules have been constructed and analyzed, and the main power and geometrical characteristics of the processes have been defined. Charge redistributions in the systems have been studied. We show that neither a hydrogen atom, nor a hydrogen molecule can be adsorbed over the hexagon center of single−layer PPAN surfaces, and in other cases chemical adsorption occurs. For adsorption over the surface of two−layer PPAN, any orientation variants of a hydrogen molecule are possible. A negative influence of nitrogen atom of the polymer surface on the efficiency of atomic hydrogen adsorption has been established, whereas its influence on the adsorption of molecular hydrogen is positive.Представлены результаты теоретического квантово−химического изучения механизмов адсорбции атомарного и молекулярного водорода на поверхности современного полимерного материала — пиролизованного полиакрилонитрила (ППАН). Рассмотрено три варианта ориентации атома водорода относительно поверхности монослоя ППАН и пять вариантов ориентации молекулы водорода относительно поверхности одно− и двухслойного ППАН, различающиеся наличием атомов азота в ближайшем окружении выбранного адсорбционного центра полимера. Построены и проанализированы профили поверхности потенциальных энергий адсорбции атома и молекулы водорода, определены основные энергетические и геометрические характеристики процессов: энергии и расстояния адсорбции, а также зарядовые перераспределения в системах. Доказано, что ни атом, ни молекула водорода не могут адсорбироваться над центром гексагона поверхности однослойного ППАН, в остальных случаях реализуется химическая адсорбция. Для адсорбции над поверхностью двухслойного ППАН адсорбция возможна для всех вариантов ориентации молекулы водорода. Установлено негативное влияние атома азота поверхности полимера на эффективность адсорбции атомарноговодорода и позитивное влияние на адсорбцию молекулярного водорода

Особенности действия брассиностероидов на растения в условиях солевого стресса

The dependence of the protective effect of brassinosteroids (BS) in a wide range of concentrations on the growth of the root system of fiber flax (Linum usitatissimum L.) and spring barley (Hordeum vulgare L.) seedlings under salt stress was studied. A narrow range of BS concentrations was revealed, in which they cause a weakening of the inhibitory effect of salinity on the root system of seedlings. An almost complete coincidence of the BS concentration ranges was noted, in which the maximum stress-protective effect of phytohormones was observed for the both crops (6,9 ⋅ 10–7–5,9 ⋅ 10–8 М for fiber flax and 2,8 ⋅ 10–7–2,4 ⋅ 10–8 М for spring barley). In the experiment with winter wheat (Triticum aestivum L.), which lasted 19 days, already on the 6th day before the seedlings were placed under stress conditions, the elongation of the seedlings treated with exogenous brassinosteroids was noted. By the end of the experiment (in the second leaf unfolding phase), all brassinosteroids showed a pronounced protective-stimulating effect under the salinity conditions that depended on the chemical structure of the hormone and changed in the brassinolide &gt; homobrassinolide &gt; homocastasterone &gt; epibrassinolide series.Исследована зависимость протекторного действия брассиностероидов (БС) в широком диапазоне концентраций на рост корневой системы проростков льна-долгунца (Linum usitatissimum L.) и ярового ячменя (Hordeum vulgare L.) в условиях солевого стресса. Выявлены узкие диапазоны концентраций БС (6,9 ⋅ 10–7–5,9 ⋅ 10–8 М для льна-долгунца и 2,8 ⋅ 10–7–2,4 ⋅ 10–8 М для ярового ячменя), в которых они вызывают ослабление ингибирующего эффекта засоления на корневую систему проростков. Отмечено практически полное совпадение диапазонов концентраций БС, в которых наблюдалось максимальное стресс-протекторное действие фитогормонов для обеих культур. В опыте с озимой пшеницей (Triticum aestivum L.), длившемся 19 суток, уже на 6-е сутки, до помещения растений в стрессовые условия, было отмечено удлинение проростков, обработанных экзогенными брассиностероидами, а к концу эксперимента (в фазу развертывания второго листа) все брассиностероиды показали выраженный защитностимулирующий эффект в условиях засоления, зависящий от химической структуры гормона и изменяющийся в ряду брассинолид &gt; гомобрассинолид &gt; гомокастастерон &gt; эпибрассинолид.