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Effect of Deformation Temperature on the Microstructure of Hard Magnetic Fecr22co15 Alloy Subjected to Tension Combined with Torsion Deformation Modes

100%
Korneva A., Sztwiertnia K., Korznikova G., Korznikov A.
Archives of Metallurgy and Materials
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2013
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issue 2
2
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Thermal Stability of Nanocrystalline Ni

100%
Korznikov A., Pakieła Z., Kurzydłowski K.
Acta Physica Polonica A
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2002
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vol. 102
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issue 2
265-271
EN
Ultrafine-grained structure with grain size of about 100 nm was obtained in nickel by deformation under a pressure of 7 GPa in Bridgman anvils. The structure evolution in ultrafine-grained nickel was studied by residual resistance, transmission electron microscopy, X-ray diffraction, and microhardness measurements. It was established that the evolution of the structure upon heating of ultrafine-grained nickel may be divided into three stages. Stage A corresponds to temperatures below 453 K and is characterised by an insignificant decrease in the resistivity and microhardness. At this stage, a decrease in the internal stresses is not accompanied by grain growth. Stage B, corresponding to the temperatures range of 453-513 K, is characterised by an abrupt decrease in the resistivity and hardness, disappearance of the internal stresses, and by an intense grain growth. Stage C (above 523 K) corresponds to an insignificant increase in the resistivity and further decrease in the hardness.
3
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Grain-Subgrain Structure and Vacancy-Type Defects in Submicrocrystalline Nickel at Low Temperature Annealing

76%
Kuznetsov P., Lider A., Bordulev Y., Laptev R., Rakhmatulina T., Korznikov A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
714-717
EN
Scanning tunneling microscopy, positron annihilation and X-ray diffraction were applied for the study of annealing of submicrocrystalline nickel prepared by equal channel angular pressing. Several processes were revealed in the structure of submicrocrystalline nickel on different scale levels during annealing in the range Δ T=(20÷360)°C. A decrease of grain nonequiaxiality and further structure refinement were observed with a temperature increase in the range Δ T=(20÷180)°C. Subgrain growth with maximum =60 nm at 120°C occurred on the lower scale level within the same temperature range. Grain growth and microstress decrease in submicrocrystalline nickel observed at T>180°C indicate the beginning of recrystallization. The main positron trap centers were identified in submicrocrystalline nickel within different temperature ranges. In as-prepared samples positrons are trapped at dislocation-type defects and vacancy clusters that can include up to 5 vacancies. At the annealing temperature Δ T=(20÷180)°C positrons are trapped at low-angle boundaries enriched by impurities. Within the range Δ T=(180÷360)°C the dominant trap is dislocations.
4
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Composition and Microstructure of the Al-Multilayer Graphene Composites Achieved by the Intensive Deformation

64%
Czeppe T., Korznikova E., Ozga P., Wrobel M., Litynska-Dobrzynska L., Korznikova G., Korznikov A., Czaja P., Socha R.
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vol. 126
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issue 4
921-927
EN
The paper presents results of the studies concerning aluminum-graphene composites produced with use of step technique; first mechanical alloying of Al and graphene powders and later intensive deformation by the high pressure torsion. As a result small, thin and round samples of composites, about 10 mm in diameter were achieved. For comparison similar samples not containing graphene were investigated. The X-ray diffraction, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy were applied to study composites structures and analyze graphene content and atomic bonds. The Raman spectroscopy method suggested multilayer graphene, which could also be identified as the defected nano-graphite as a component of the composite structure as well as some small content of the aluminum carbides. The highly dispersed microstructures of aluminum matrices were identified with the transmission electron microscopy, showing difference between the samples produced with the increased number of rotations, leading to the increased deformation realized. This method revealed carbon and aluminum oxides in large amounts which is interpreted as a surface effect. This method suggested also formation of the carbon-metal and carbon-metal- oxygen atomic bonds, which might partially result from formation of the carbides.
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