polymorphic transformations
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2021 ◽  
Vol 130 (24) ◽  
pp. 245902
Author(s):  
Semen Murzov ◽  
Sergey Ashitkov ◽  
Evgenia Struleva ◽  
Pavel Komarov ◽  
Vasily Zhakhovsky ◽  
...  

Author(s):  
Ирина Гусейновна Шебзухова ◽  
Людмила Павловна Арефьева

На базе электронно-статистического метода показана связь и проведена оценка поверхностной энергии и работы выхода электрона граней кристаллов лития с учетом дисперсионного, поляризационного и осцилляционного взаимодействия атомов поверхностного слоя. Считалось, что кристаллическая решетка не имеет дефектов. Модифицированы выражения поправок и аналитического соотношения, связывающего работу выхода электрона и поверхностную энергию с учетом типа кристаллической решетки и ориентации граней. Рассчитана работа выхода электрона и поверхностная энергия гладких граней при предельных температурах существования полиморфных фаз лития. Установлено влияние полиморфных превращений и температуры на анизотропию. Температурный коэффициент работы выхода электрона бездефектного кристалла положителен и составляет порядка 0,1-1 мэВ. Результаты расчетов хорошо согласуются с экспериментальными данными для поликристаллов. On the basis of the electronic-statistical method, a relationship is obtained and the surface energy and the work function of the electron of the faces of lithium crystals are estimated, taking into account the dispersion, polarization, and oscillatory interactions of the atoms of the surface layer. It was assumed that the crystal lattice has no defects. The expressions for the corrections and an analytical relationship between the work function of the electron and the surface energy are modified taking into account the type of the crystal lattice and the orientation of the faces. The work function of the electron and the surface energy of smooth faces are calculated at the limiting temperatures of the existence of polymorphic lithium phases. The influence of polymorphic transformations and temperature on the anisotropy is established. The temperature coefficient of the work function of an electron in a defect-free crystal is positive and amounts to about 0,1-1 meV. The calculation results are in good agreement with the experimental data for polycrystals.


Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3172
Author(s):  
Alisher E. Kurakhmedov ◽  
Mahambet Alin ◽  
Adilet M. Temir ◽  
Igor A. Ivanov ◽  
Yeugeniy V. Bikhert ◽  
...  

The purpose of this study is to assess the effect of doping ZrO2 ceramics with MgO on radiation swelling and polymorphic transformations, as a result of irradiation with heavy ions. Interest in these types of materials is due to the great prospects for their use as structural materials for new-generation reactors. The study established the dependences of the phase composition formation and changes in the structural parameters following a change in the concentration of MgO. It has been established that the main mechanism for changing the structural properties of ceramics is the displacement of the cubic c-ZrO2 phase by the Zr0.9Mg0.1O2 substitution phase, which leads to an increase in the stability of ceramic properties to irradiation. It has been determined that an increase in MgO concentration leads to the formation of an impurity phase Zr0.9Mg0.1O2 due to the type of substitution, resulting in changes to the structural parameters of ceramics. During studies of changes in the strength properties of irradiated ceramics, it was found that the formation of a phase in the Zr0.9Mg0.1O2 structure leads to an increase in the resistance to cracking and embrittlement of the surface layers of ceramics.


Author(s):  
Rongfeng Guan ◽  
Pan Wang ◽  
Yang Song ◽  
Viktor N. Staroverov

2021 ◽  
Vol 1038 ◽  
pp. 25-32
Author(s):  
Oleksii Kaglyak ◽  
Bohdan Romanov ◽  
Kateryna Romanova ◽  
Nataliia Tsapko

The article analyses the effect of temperature distribution at different points of the irradiation zone on the nature of leakage of structural-phase transformations. The results of the X-structural analysis are given, which shows the presence of martensite and residual austenite in the treatment zone. The peculiarities of structural-phase transformations during laser heating are studied and their effect on strain value during laser shaping is determined. The results of experimental studies are given, according to which, if the mechanisms for forming the temperature gradient and polymorphic transformations (for 65G steel) operate in parallel, the amount of deformation is one third of the sample for which only the temperature gradient mechanism works (12Х18N10Т steel).


Author(s):  
Ankit Singh ◽  
Maurya Sandeep Pradeepkumar ◽  
Deepak Kumar Jarwal ◽  
Satyabrata Jit ◽  
Sandip Bysakh ◽  
...  

Author(s):  
П.В. Бахматов ◽  
Е.Е. Тишкова

В работе приведены результаты экспериментального исследования способа автоматической сварки под слоем флюса плоских листовых конструкций обеспечивающего существенное снижение уровня сварочных деформаций, равномерность распределения твердости, как по поверхности стыкуемых кромок, так и в поперечном сечении сварного шва, минимизацию зон термического влияния и отсутствие в них закалочных структур. Способ основан на сдерживании процесса последовательного прохождения полиморфных превращений в формируемом металле шва до момента окончания сварки и последующем отпуске всего соединения. Полученные сварные соединения, удовлетворяют требованиям нормативной документации, регламентирующей их форму и размерность. Установлено, что применение этого способа позволяет осуществлять одностороннюю однопроходную автоматическую сварку без разделки кромок и зазора на режимах традиционной двусторонней сварки, а также существенно повысить глубину проплавления. Для реализации процесса разработан лабораторный стенд, позволяющий осуществлять автоматическую сварку без установки сварочного трактора на поверхность соединяемых деталей. Показана неэффективность расчетных методов определения напряжений и деформаций при сварке под слоем флюса. The paper presents the results of an experimental study of the method of automatic welding under a layer of flux of flat sheet structures, which provides a significant reduction in the level of welding deformations, uniformity of hardness distribution, both on the surface of butting edges and in the cross section of the weld, minimization of heat-affected zones and the absence of hardening structures. The method is based on restraining the process of sequential passage of polymorphic transformations in the formed weld metal until the end of welding and subsequent tempering of the entire joint. The resulting welded joints meet the requirements of the normative documentation governing their shape and dimension. It was found that the use of this method allows one-sided single-pass automatic welding without cutting edges and a gap in the modes of traditional two-sided welding, as well as significantly increasing the penetration depth. To implement the process, a laboratory stand has been developed that allows automatic welding without installing a welding tractor on the surface of the parts to be joined. The inefficiency of calculation methods for determining stresses and strains in submerged arc welding is shown.


2021 ◽  
Vol 2021 (2) ◽  
pp. 72-78
Author(s):  
A. O. Makudera ◽  
◽  
S. M. Lakiza ◽  

Based on the analysis of literature data from experimentally constructed phase diagrams of Y2O3 − Ln2O3 systems (Ln = Tb − Lu), as well as temperatures of polymorphic transformations of rare earth oxides (REE), tentative phase diagrams of Y2O3 − Ln2O3 systems (Ln = Tb − Lu) were constructed in wide intervals of temperatures and concentrations. Prediction of the binary phase diagrams structure of yttria − yttrium subgroup lanthanides systems was carried out on the basis of three principles: 1. Since double systems are formed by lanthanide oxides of one (yttrium) subgroup, it is very likely that in such systems continuous solid solutions will be formed between the components. 2. Intermediate binary phases are not formed in these systems. 3. The formation of continuous solid solutions occurs with a decrease in the temperatures of phase transformations in the solid state to a minimum shifted towards a lower transformation temperature of the system component. The forecast of the Y2O3 – Ln2O3 systems phase diagrams structure, where Ln = Tb – Lu, indicates the complete solubility of the components in the liquid and solid states. Binary compounds in the considered systems are not predicted. Phase transformations in the solid solutions on the basis of polymorphic modifications X, H, A, B and C of lanthanide oxides cascade at high temperatures by the peritectoid mechanism. Below 1850 °C regions of solid solutions with cubic C-structure of REE oxides are formed in the whole range of concentrations in the systems. Key words: REE oxides, yttria, polymorphs of REE oxides, phase diagram.


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