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1
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Phase Identification of Nanometric Precipitates in AlSi9Cu Alloy after Remelting by Laser Beam

100%
Pawlyta M., Labisz K., Matus K.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
827-829
EN
The aim of presented paper is an investigation of the structure changes in AlSi9Cu alloy after remelting by a laser beam. Scanning transmission electron microscopy was applied for structure characterization and precipitates phase identification. In the raw material, precipitates were larger and during remelting such precipitates were dissolved and very fast crystallization came next. Observed precipitates are generally uniform: in size, shape, and chemical composition. Generally, after remelting precipitates are not uniformly distributed in the whole sample but areas with dense, nanometric precipitates are common. Numerous volumes with elongated Ti precipitates, identified as Ti(Al_{1-x}Si_{x})₃, were found. Observed precipitate can strongly affect material properties (even in a case of law Ti concentration) because it may act as a crystal nucleus for other phases.
2
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Study of Dislocation Substructures in High-Mn Steels after Dynamic Deformation Tests

100%
Śmiglewicz A., Moćko W., Rodak K., Bednarczyk I., Jabłońska M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
942-945
EN
The article presents the dynamic mechanical properties of two types of high manganese austenitic TWIP steels. The investigations were carried out for the wide range of strain rates from 10¯² s¯¹ up to 4×10³ s¯¹ using servo-hydraulic testing machine and split Hopkinson bar for the quasi-static and dynamic loading regime, respectively. The mechanical properties at different strain rates like yield strength and true stress were calculated out on the base of the results of impact tests. In the next step, the microstructure of the analyzed steels after different deformation rates were observed by scanning transmission electron microscopy technique in order to disclose a dislocation structures and mainly the TWIP effect. In the studies observed that with the strain rate increasing yield strength as well as true stress for 0.3 true strain increasing in both steels. The microstructure observations reveal the influence of strain rate on the structure evolution for analyzed steels.
3
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The Structural Characterization of Ni-Ti-Zr Metallic Glass

100%
Katuna Y., Lisnichuk M., Saksl K., Girman V., Gamcová J., Balga D., Ďurišin M., Kováč J., Sovák P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
750-752
EN
Metallic glasses, in contrast to its crystalline counterparts, exhibit unique mechanical and structural properties, which make them attractive for practical applications. Especially Ni-Ti-Zr metallic glass is a promising alloy for micromechanical systems because of its known shape memory properties. Shape memory effect is connected with structural phase transformation. In this paper, the ambient-temperature-structure of Ni-Ti-Zr metallic glass is investigated using transmission electron microscopy and synchrotron X-ray diffraction, the surface and chemical analysis is documented using scanning electron microscopy. Thermal stability of the alloy has been determined using differential scanning calorimetry.
4
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The Effect of σ-Phase Formation on Long-Term Durability of Welding Joints in SUPER 304H Steels

88%
Horváth J., Král P., Janovec J.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
960-962
EN
Article presents results on the analysis of secondary phases formed in the medium-term static isothermal ageing welding joints of a SUPER 304H (675°C/2×10⁴ h). The investigations of the precipitates were focused on the occurrence of σ-phase because its formation leads to significant deterioration of mechanical properties. The microstructure was investigated on microscopic level by scanning/transmission electron microscopy. The distribution and quantification of brittle σ-phase were studied on macroscopic level by color etching method using light optical microscopy. The effect of microstructural changes (σ-phase formation) on the impact strength of an aged base material was investigated. For comparison impact tests on received state material were also performed. The results showed that long-term ageing led to the significant reduction of impact strength as a result of the formation of the σ-phase. It was found that the σ-phase distribution is influenced by welding process. The influence of brittle σ-phase on long-term durability of the degraded steel regarding its insufficient impact strength has been discussed.
5
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Characterization of CeO₂, ZrO₂, and CeZrO₂ Crystals on CNT

88%
Matus K., Łamacz A., Liszka B.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
966-968
EN
Carbon nanotubes are increasingly being used as a support for catalyst particles. Carbon nanotubes are also used for filtering and reduction, their widespread use due to the high surface area which allows for attachment to the surface of carbon nanotubes a large amount of metallic (Ni, Fe, Pt, etc.) or oxide particles, serving as catalysts. The use of ceria-zirconia mixed oxide deposited on the surface of the nanotubes has not yet been sufficiently examined. Scanning transmission electron microscope with high-angle annular dark-field imaging and high-resolution transmission electron microscopy imaging were used as primary research techniques. Conducted research using high-angle annular dark-field imaging allows determining that catalyst particles have a regular shape which is the best from the standpoint of catalysis. Using a fast Fourier transform: and diffraction pattern has identified the catalyst particles as CeZrO₂.
6
Content available remote

Analytical Electron Microscopy Studies of the CMSX-4 Single Crystal Superalloy Subjected to High Temperature Annealing

88%
Dubiel B., Indyka P., Kalemba-Rec I., Moskalewicz T.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1375-1378
EN
The aim of the present work is to investigate the development of the γ/γ' microstructure and the changes in chemical composition of γ and γ' phases during high temperature annealing of CMSX-4 superalloy at a temperature of 1100°C in the time range from 500 to 2500 h. The studies were performed by means of scanning electron microscopy and the modern scanning-transmission electron microscopy with Super-X EDS system of four SDD detectors. Results of scanning electron microscopy and scanning-transmission electron microscopy analyses have shown that the microstructure of CMSX-4 superalloy is unstable during ageing at high temperature and the coalescence of cuboidal γ' precipitates was observed. Energy dispersive X-ray microanalysis revealed the distribution of particular alloying elements in the γ and γ' phases and the differences in their concentration in the function of the annealing time.
7
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Analytical Electron Microscopy Investigation of Topologically Close-Packed Phases in CMSX-4 Single Crystal Superalloy

75%
Dubiel B., Indyka P., Kalemba-Rec I., Moskalewicz T.
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EN
In this work the topologically close-packed phases precipitated during annealing of CMSX-4 single-crystal superalloy at temperature 1100°C were investigated. Microstructural analyses were carried out by means of scanning- and transmission electron microscopy as well as scanning-transmission electron microscopy in high angle annular dark field mode. Chemical composition in nanoareas was determined using energy dispersive X-ray spectroscopy. Scanning electron microscopy investigation has shown that the topologically close-packed precipitates were formed already after 50 h of annealing at temperature 1000°C. With prolongation of the annealing time up to 2500 h the change of the morphology of topologically close-packed particles from blocky to needle-like occurred. Selected area electron diffraction analysis indicated that the topologically close-packed precipitates are the orthorhombic P phase. Quantitative energy dispersive X-ray spectroscopy analysis revealed that the topologically close-packed precipitates are enriched mostly in Re and W.
8
Content available remote

TEM Study of the Structural Properties of Nanowires Based on Cd, Zn, Te grown by MBE on Silicon Substrates

51%
Kaleta A., Kret S., Sanchez A., Bilska M., Kurowska B., Szczepańska A., Płachta J., Wojnar P., Wojciechowski T.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1399-1405
EN
In this work we report on the atomic structures, elemental distribution, defects and dislocations of three types of semiconductor nanowires: ZnTe, CdTe, and complex ZnTe/(Cd,Zn)Te core/shell hetero-nanowires grown by a molecular beam epitaxy on (111) Si substrate using a vapor-liquid-solid mechanism. The structural properties and the chemical gradients were measured by transmission electron microscopy methods. The nanowires reveal mainly sphalerite structure, however wurtzite nanowires were also observed.
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