I. M. Safarov

I. M. Safarov
Institute for Metals Superplasticity Problems of Russian Academy of Sciences | IMSPRAS · Transmission and Scanning Electron Microscopy

Doctor of Philosophy

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60
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517
Citations

Publications

Publications (60)
Article
The Heusler alloys demonstrate magnetically induced strain and magnetocaloric properties, but the mechanical properties are poor. Therefore, in this work, the influence of thermomechanical treatment on the properties of Ni-Mn-Ga-Si Heusler alloys is considered. The effect of multi-axial isothermal forging on functional properties of the Ni2.30Mn0.7...
Article
Heusler alloys demonstrate various effects, such as the ferromagnetic shape memory effect, the magnetocaloric effect, etc. But these alloys are also liable to destruction during multiple cycles of martensitic transformation. In order to increase stability of functional properties of the alloys, thermo-mechanical treatment by various methods is carr...
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It is shown that in low carbon steel, the structure after the controlled rolling comprises grains of ferrite and carbides. The average grain size of ferrite was 2.5 µm, the carbide size varied from 1 to 5 µm. Additional warm rolling led to the formation of a fibrous ultrafine-grained (UFG) structure with an average grain/subgrain size about 0.3 µm,...
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The work presents the comparative analysis of the microstructure and character of martensitic transformation in Heusler Ni-Mn-Ga alloys subjected to plastic deformation by forging and complex treatment by forging with subsequent extrusion. It is shown that the treatment by forging leads to the formation of a bimodal structure with large grains of s...
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The formation of a sharp crystallographic texture in a Ni–Mn–Ga Heusler alloy by the multiple isothermal forging has been studied. An analysis of the thermal expansion near the martensitic transformation temperatures in the as-cast and forged states of the alloy shows that the thermomechanical treatment leads to an increase in the anisotropy of the...
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В работе исследовали формирование острой кристаллографической текстуры в сплаве Гейслера системы Ni−Mn−Ga после всесторонней изотермической ковки сплава. Анализ термического расширения в области температур мартенситного превращения в исходном литом и кованном состояниях сплава показал, что деформационная обработка приводит к возрастанию анизотропии...
Article
The results of investigation of the microstructure of two polycrystalline Ni-Mn-Ga alloys subjected to thermo-mechanical treatment by multiple isothermal forging and extrusion are presented. Alloy forging at a temperature of 680°C and 700°C leads to the formation of a bimodal structure which has large grains of several hundred micrometers surrounde...
Article
The temperatures ductility of the polycrystalline Ni2.19Fe0.04Mn0.77Ga alloy was investigated. The analysis of the temperature dependence of the specific magnetization shows that temperatures of the martensitic and magnetic phase transformations have the following values: MF=325 K, AS=343 K, TC=365 K. The differential scanning calorimetry shows tha...
Article
The plastic behavior during deformation by upsetting and its effect on the microstructure in the polycrystalline Ni2.19Fe0.04Mn0.77Ga alloy are studied. The temperatures of martensitic and magnetic phase transformations were determined by the method for analyzing the temperature dependence of the specific magnetization as MF = 320 K, AS = 360 K, an...
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Исследованы пластическое поведение в процессе деформации осадкой и ее влияние на микроструктуру в поликристаллическом сплаве Ni 2.19 Fe 0.04 Mn 0.77 Ga. Методом анализа температурной зависимости удельной намагниченности установлены температуры мартенситного и магнитного фазовых превращений, которые имеют следующие значения: M F =320 K, A S =360 K,...
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The paper presents the results of plastic deformation by the multiple isothermal forging on microstructure and martensitic transformation in polycrystalline Ni54.1Mn19.6Ga24.6Si1.7 alloy. The method of plastic deformation was applied to Heusler alloys for the first time. By recording the temperature dependence of thermal expansion in the field of t...
Article
The paper presents the results of studies on the effect of deformation nanostructuring of cathodes from aluminum alloy Al-6%Mg on the glow gas-discharge current in a discharge device. Microstructure and work function of nanostructured alloy are studied. It is shown that a decrease of the work function as a result of alloy nanostructuring leads to a...
Article
The structure and mechanical properties of ultra-low carbon interstitial-free (IF) steel in the annealed state, after warm and cold rolling, and as a component of seven-layer steel–aluminum composite have been studied. A comparative analysis of the results of structural studies using optical microscopy and scanning and transmission electron microsc...
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The structure and properties of a polycrystalline Ni–Mn–In Heusler alloy have been studied after a plastic deformation by upsetting. An analysis of points of a martensitic and magnetic phase transformations shows that the martensite transformation takes place at temperatures lower than the Curie point. At high temperatures in the range 930–1110 K t...
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The paper reports on the investigation of the effect of various methods of plastic deformation on the structure, texture and mechanical properties of low carbon 12GBA steel. It is found that multiple isothermal forging results in formation of equiaxed ultrafine-grained (UFG) structure with a uniform distribution of the second phase, the size of whi...
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The effect of all-round isothermal forging on the structure and mechanical properties of low-carbon steel 12GBA is investigated.
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The influence of annealing temperature on ultrafine-grained structure (UFG) of low-carbon steel 05G2MFB, produced by multiple isothermal forging (MIF) and warm rolling is investigated. Following 1-hour annealing (from 20 to 550°С), the fibrous UFG-structure formed as a result of rolling remains virtually the same. The equiaxial UFG-structure is fou...
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Composites with a copper matrix, reinforced by carbon nanotubes, have been produced by the multistage method including functionalization of carbon nanotubes, their dissolution, mixing with a copper powder, preliminary warm isostatic compaction, and severe plastic deformation by torsion. The microstructure and microhardness of composites containing...
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Composites with a copper matrix, reinforced by carbon nanotubes, have been produced by the multistage method including functionalization of carbon nanotubes, their dissolution, mixing with a copper powder, preliminary warm isostatic compaction, and severe plastic deformation by torsion. The microstructure and microhardness of composites containing...
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This paper presents results of a research on the effect of warm rolling on structure and mechanical properties of the low-carbon pipe steel. The warm rolling results in formation of anisotropic ultra-fine grained (UFG) structure with average grain / subgrain size 0.5 μm in transverse direction and 20—30 μm along the rolling direction. The formation...
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The results of a study of the martensitic transformation in the polycrystalline Ni52Mn24Ga24 alloy in different structural states are presented in the article. In the initial state in the alloy magnetic and martensitic phase transformation is observed with the following characteristic points: MS=25°C; MF=15°C; AS=35°C; AF=45°C; TC=127°C. The alloy...
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The effect of severe warm rolling on the structure and mechanical characteristics of the 12GBA low-carbon steel has been studied. A fibrous ultrafine-grained structure has been formed; the average transverse size of structural elements was 0.5 μm and the length of fibers in the longitudinal section was 20–25 μm. An analysis of this ultrafine-graine...
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The complex deformation processing effect on the structure and mechanical properties in the low-carbon steel 05G2MFB is investigated. The complex deformation processing of the low carbon steel was obtained ultrafine-grained (UFG) structure with an average size of grains of 0.4 μm. The formation of UFG structure leads to in to two times increase in...
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The ion-electron emission of nanocrystalline aluminum alloy Al + 6% Mg is investigated. The nanocrystalline structure in the alloy was manufactured by torsional deformation under quasi-hydrostatic pressure. The ion-electron emission coefficient for the nanocrystalline alloy sample is higher than that of the coarsely crystalline sample. The increase...
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The electron work function of nickel with various grain sizes has been studied. It has been shown that the work function decreases as the specific length of grain boundaries in nickel increases with decreasing average grain size. It has been found that the transformation of grain boundaries from a nonequilibrium to equilibrium state leads to an inc...
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1 Тольяттинский государственный университет, Тольятти 2 Тольяттинский филиал Самарского государственного аэрокосмического университета, Тольятти 3 Институт проблем сверхпластичности металлов РАН, Уфа Проанализированы технологические возможности элек-тролитно-плазменной обработки. Представлены резуль-таты многоэтапной электролитно-плазменной полиров...
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It is shown that the intensive warm rolling of 12GBA low carbon steel leads to the formation of ultrafine-grained (UFG) structure with an average grain size of 0.5 µm in transverse section and to two times increase in strength by comparison to the initial coarse-grained (CG) state. Impact tests have shown an increase of fracture strength in fibrous...
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The effect of intense warm deformation on the structure and mechanical properties of low-carbon 12GBA steel was investigated. A submicrocrystalline (SMC) structure with an average element size of 0.3 μm was formed in the steel by isothermal overall forging. The formation of the SMC structure resulted in a sharp increase in strength by a factor of t...
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The submicrocryctalline structure of the 12GBA low carbon steel was processed by multi-axis isothermal forging. The average grain size was about of 0.3 µm. The submicrocryctalline steel has three times higher strength than the coarse-grained steel andsufficiently high ductility and impact strength. Subsequent annealing leads to a slight lowering of...
Article
The temperature dependence of thermal expansion of the Ti-49.8 at % Ni alloy has been measured after rolling at temperatures of 470, 570, 670, 770, and 870 K. The maximum dilatation jump during the martensitic phase transition has been observed for the samples rolled at 570 and 670 K. A fragmented structure, in which the phase transformations are h...
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Commercially pure (99.9%) copper was severe plastically deformed by equal-channel angular pressing (ECAP) following route-Bc in three different processing regimes in order to obtain ultrafine-grained (UFG) microstructures leading to improved mechanical properties. In regime-1, the billets were processed at room temperature up to eight passes. The b...
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The effect of deformational nanostructuring on the electron work function for nickel is investigated. The current-voltage characteristic of the gas discharge with nanocrystalline nickel as the cold cathode is measured. It is found that the electron work function is considerably reduced and the ion-electron emission current in the gas discharge incr...
Article
Temperature dependences of the magnetization and thermal expansion coefficient of the Fe-36% Ni invar alloy in different structural states obtained upon plastic deformation by torsion under a quasihydrostatic pressure followed by annealing at different temperatures are studied. A decrease in the thermal expansion coefficient of the invar in a tempe...
Article
Temperature dependencies of saturation magnetization and temperature coefficient of linear expansion for the Fe-36%Ni alloy have been studied in different structural states obtained by severe plastic torsion straining under quasi-hydrostatic pressure and following annealing at different temperatures. The studies have revealed the decrease in the co...
Article
This work is devoted to the investigation of the microstructure evolution in the 2219 aluminum alloy (Al-6.4% Cu-0.3% Mn-0.18% Cr-0.19% Zr-and 0.06% Fe) upon severe plastic deformation (SPD) in a wide temperature range. Special attention is paid to the mechanisms of formation of new grains. The severe plastic deformation was performed at room tempe...
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Numerous investigations have demonstrated that intense plastic deformation is an attractive procedure for producing an ultrafine grain size in metallic materials. Torsional deformation under high pressure and equal-channel angular extrusion are two techniques that can produce microstructures with grain sizes in the submicrometer and nanometer range...
Article
The fine structure and microhardness of the white layer formed at the surface of railroad rails under service conditions were studied. This layer was found to have an ultrafine-grained structure with an average ferrite grain size of 200 nm. The initial cementite framework in the layer is broken, and the hardness increases by a factor of 3.5 as comp...
Article
The formation of a submicron fibrous (SMF) structure in low carbon low alloy steels under severe warm rolling is investigated. It is shown that by varying modes of deformation one can obtain structures with either equilibrium or nonequilibrium grain boundaries (GBs). It is established that SMF structure provides for a sharp increase in strength pro...
Article
It has been found that during severe plastic deformation of Armco iron and two stainless steels the structure develops from a cell structure to a fragmented structure with high angle misorientations and a mean grain size of 100 nm. The correlation between structure changes and microhardness has been demonstrated. The thermal stability of ultrafine...
Article
A study was made into structure evolution in armco-iron, stainless austenitic steel A/S/316L and stainless ferritic steel type 13Kh25T under torsional strain. It is shown that shear strain under quasihydrostatic pressure (5GPa) at room temperature results in subsequent change of three types of dislocation structures. The sequence of transformation...
Article
Samples of Fe-1.2%C steel were subjected to high torsion straining under a quasi-hydrostatic pressure. Severe plastic deformation caused complete dissolution of the cementite phase. After large strains a highly dispersed structure with a mean particle size of 20 nm was formed, and the hardness of samples reached 11.7 GPa, which was 2.5 times higher...
Article
Cold plastic deformation of high-carbon U12A steel under 10 GPa pressure leads to the formation of a nanocrystalline structure with an average size of fragments of 20 nm. At the same time, cementite lamellae are completely dissolved, and a supersaturated solid solution of carbon in iron is the result. The hardness level obtained for Steel U12A in t...
Article
Low-carbon steels alloyed with manganese, nickel and molybdenum have been taken as an example to investigate the effect of tempering within the range of 200-600°C on strain hardening and resistance to failure under impact and static loading. The tempering at 500-600°C is found to result in a decrease of fracture toughness, strain hardening degree a...
Article
By the methods of diffraction electron microscopy and X-ray structure analysis, the changes of structure and phase composition of oxidized iron particles is investigated in their compaction by means of intense deformation (e=5) at high pressure. Such treatment allows to obtain monolithic specimens and results in oxide phase dissolution, thus formin...
Article
1. Rolling at temperatures above the recrystallization temperature with high levels of rolling makes it possible to obtain in low-carbon steels an improved submicron-grain structure with low dislocation density and a grain size of 0.8 μm, and at a temperature below the recrystallization temperature it leads to an incomplete submicron-grain structur...
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Possibility of strength increase has been considered for low-alloy 03KhGSF and 20GSF steels on retention of high toughness and ductility by methods of production of submicrograined structure. Rolling at temperatures higher than recrystallization temperatures with great degrees permits to receive perfect submicrograined structure with low density of...
Article
Nanocrystalline structure formation was studied in low-carbon low-alloy steels under deformation by warm rolling as well as its influence on tensile properties. Fine-grained microstructure was produced by rolling in a ferrite-pearlite range (520° C) with deformation degree of 90 %. This treatment resulted in grain and subgrain size of 0.7 μ and in...
Article
The surface of the ultra-disperse iron powder particles was oxidized being in contact with the air. The powder was compacted under pressure plus torsion straining. The oxide film was found to dissolve during intensive deformation under pressure. A high degree of cold working of the resulting system Fe-O results in the formation of a fairly high-dis...

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Project (1)
Project
The goal of project is increasing the thermostability of physical properties and microstructure after repeated cycles of the martensitic transformation.