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  1. 29 Acta Physica Polonica A

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  1. 1 2018

  2. 3 2017

  3. 5 2016

  4. 6 2015

  5. 2 2014

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  1. 3 Rodak K.

  2. 3 Urbańczyk-Gucwa A.

  3. 2 Ali Cetinkara H.

  4. 2 Bohlen J.

  5. 2 Chmelík F.

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1
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Mechanical Properties of Nanocrystalline Tetragonal Zirconia Stabilized with CaO, MgO and Y_2O_3

100%
Sahin O., Demirkol İ., Göcmez H., Tuncer M., Ali Cetinkara H., Salih Güder H., Sahin E., Rıza Tuncdemir A.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
296-298
EN
The citrate gel method, similar to the polymerized complex method, was used to synthesize homogeneous tetragonal zirconia at 1000°C. Nanocrystalline tetragonal phase has been fully stabilized at wide temperature range with 10 mol.% CaO, MgO, and Y_2O_3 addition. Scanning electron microscopy, X-ray diffraction, and microhardness tests are used to characterize synthesized materials. The grain size and dislocation density were calculated from X-ray diffraction data. The examined material exhibits indentation size effect behavior. Results revealed that the Vickers and Knoop microhardness are dependent on indentation test load. Geometrically necessary dislocation model and modified proportional resistance model are used to analyze the load dependence of the microhardness. The highest hardness values were obtained for the samples with CaO addition; however the lowest values were acquired for sample stabilized with Y_2O_3 by using both Knoop and Vickers techniques. This situation might be explained using the Hall-Petch relation.
2
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Basal to Non-Basal Transition for In-Plane Deformation of AZ31 Magnesium Alloys

100%
Balík J., Lukáč P., Kužel R.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
435-438
EN
The increases in strain hardening observed for the in-plane tensile deformation of well-aged magnesium alloy AZ31 are related to a transition from basal to non-basal slip. Based on the results of texture measurements, the double prismatic slip is proposed as the dominant secondary mechanism. The necessary fast strengthening of the basal slip is modelled by an accommodation contribution to the grain boundary resistance. The transition may be consistently modelled by involving the accommodation rather than the production of new sessile dislocations into the evolution laws for dislocation populations.
3
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Hardness Behavior of Alumina-Zirconia Nanocomposites Synthesized by Gel Process

100%
Sahin O., Hasde A., Göcmez H., Tuncer M., Ali Cetinkara H., Salih Güder H., Sahin E., Rıza Tuncdemir A.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
299-301
EN
The alumina-zirconia composites are one of the relatively good and promising candidates for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. The aim of the present work is to analyze the mechanical properties of these composites, where zirconia content was varied from 5 to 50 wt%. The citrate gel method, similar to the polymerized complex method, was used to synthesize these ceramics. Scanning electron microscopy, X-ray diffraction and microhardness tests are used to characterize synthesized materials. The examined material exhibits the behaviour of indentation size effect. Modified proportional resistance model are used to analyze the load dependence of the microhardness. X-ray diffraction analysis was used to calculation of the grain size and dislocation density. It is found that hardness is decreased when the zirconia content increases with enlargement of grain size.
4
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Finite Element Analysis of Pallet-Nail Materials Used in Pallet Joint Design for Material Handling Works

100%
Karaçalı Ö., Taner Ulguel A.
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vol. 125
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issue 2
183-185
EN
The aim of this research was to construct a nailing model based on the shape and material of the prepared nail-pallet joint. The finite element analysis was used due to the stress occurring in joining process, geometry of the nail and rigidness of the wood material. The behavior of palette system under loading was investigated according to material behavior and strain-stress distribution in this research. In order to simulate phenomena in real system, a simplified model of nail-pallet joint system was worked out. The simplifications concerned mostly geometry of nail. The nail was represented by height h = 60 mm, corresponding with thickness of pallet. The effect of numerical analysis was determination of strains and stresses in working part of the nail-pallet. Results of analysis indicate diverse values of strains and stresses distribution in working part of the nail-pallet depending on its geometry. The numerical analysis of the operational nail-pallet joint system in simulated conditions of nailing in a pallet can be a basis for optimization of cutting edge geometry of joining tools as well as for selection of their mechanical properties and suitable materials. The results of this analysis are helpful for pallet design engineers for material selection and material handling interest.
5
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Peculiarities of Plastic Deformation of SPD Al-Li Alloy at 0.5 K

100%
Shumilin S., Isaev N., Zabrodin P., Fomenko V., Grigorova T., Geidarov V.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
536-539
EN
The mechanical properties of Al-Li solid solution were studied in tensile deformation tests at extremely low temperature of 0.5 K. The purpose of this study was to investigate the flow stress and work hardening rate as well as the development of serrated (jump-like) deformation for the polycrystalline samples with different microstructure. The samples obtained by severe plastic deformation via hydroextrusion were initially tensed up to a given intermediate deformation, then unloaded, annealed to modify their microstructure, and once again deformed to fracture. The increase of the grain size and decrease of average dislocation density due to annealing were found responsible for the work hardening rate increases and the flow stress decrease in accordance with the superposition of the Hall-Petch and Taylor contributions. As opposed to the flow stress, the high ductility of the samples remains rather insensitive to the microstructure properties, apparently due to suppressed recovery processes as well as the unstable deformation mode at extremely low temperature. The high ductility makes it possible to compare the work hardening rate and the scale of jump-like plastic deformation along the stress-strain curves for samples with different microstructures. In all cases, the average amplitude of the stress jumps was observed to increase whereas the average work hardening rate decreases with deformation. The observed correlation indicates that the nature of both phenomenons follows from the dislocation density evolution processes.
6
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A Study of Defects in Iron Based Alloys by Positron Annihilation Techniques

100%
Mostafa K., De Baerdemaeker J., Segers D., Calvillo P., Van Caenegem N., Houbaert Y.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1471-1478
EN
Defects in different iron based alloys were studied at room temperature using positron annihilation techniques. In FeSi alloys, it was found that the Si content and the deformation temperature affect the positron annihilation parameters. In Fe-Mn-Si-Cr-Ni-C samples with different deformations, positron lifetime measurements were carried out before and after isochronal annealing. X-ray diffraction gave information about the different microstructural phases that exist in the deformed alloys before and after annealing. During deformation a martensiticεphase is induced. At 500°C, defects and theεmartensite phase were almost annealed out from the low deformed samples.
7
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Powder Metallurgy Preparation of Co-Based Alloys for Biomedical Applications

80%
Marek I., Novák P., Mlynár J., Vojtěch D., Kubatík T., Málek J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
597-601
EN
Co-based alloys represent very important group of materials used for medical applications. Currently, fabrication of these materials is preferentially done by casting or forming. Production by powder metallurgy techniques is less common. However, powder metallurgy fabrication of these alloys brings advantages such as reduced machining, possibility of alloying by high-melting elements, preparation of nanocrystalline materials with enhanced mechanical properties or producing of porous alloys with improved ability to integrate into issues. In this work, our attention was focused on fundamental preparation of an CoCrMo alloy by two methods of powder metallurgy. In the first method, pure metallic powders were mixed, pressed and sintered in vacuum furnace. The second applied technology consisted of mechanical alloying using planetary ball mill and compaction by spark plasma sintering technique. A series of samples was prepared under various conditions by these procedures. Dependence of microstructure, phase composition and mechanical properties of prepared samples on fabrication conditions (milling parameters, sintering temperature etc.) was studied. Obtained results were compared with properties of commercial cast cobalt alloy used for medical applications.
8
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Elastic-Plastic Transition in MBE-Grown GaSb Semiconducting Crystal Examined by Nanoindentation

80%
Majtyka A., Trębala M., Tukiainen A., Chrobak D., Borgieł W., Räisänen J., Nowak R.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1131-1133
EN
The present paper concerns the elastic-plastic nanodeformation of Te-doped GaSb crystals grown by molecular beam epitaxy on the n-type of GaSb substrate. The conventional analysis of nanoindentation data obtained with sharp triangular (Berkovich) and spherical tip revealed the elastic modulus (E=83.07± 1.78 GPa), hardness (H=5.19±0.25 GPa) and "true hardness" (H_{T}=5.73±0.04 GPa). The registered pop-in event which indicates the elastic-plastic transition in GaSb crystal points towards the corresponding yield strength (σ_{Y}=3.8±0.1 GPa). The origin of incipient plasticity in GaSb crystal is discussed in terms of elastic-plastic deformation energy concept.
9
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Methods and Ways of Piezoelectric Accelerometers Fastening on the Objects of Research

80%
Korobiichuk I., Bezvesilna O., Kachniarz M., Koshovyj M., Kvasnikov V.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
1112-1115
EN
Methods and ways of piezoelectric measuring converters fastening on the objects of research are considered in the article. Piezoelectric accelerometers are sensors of a contact type, they have a mechanical contact with the object of research. The peculiarity of such connection is the fact that the object immediately has an influence on the output signal of the accelerometer. Therefore, study of methods and ways of piezoelectric accelerometers fastening on the objects of research is, undoubtedly, topical. Their advantages and disadvantages are specified. Recommendations about the choice of the way of piezoelectric measuring converters fastening on the objects of research depending on the operating conditions are made.
10
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Acoustic Emission Study of Plastic Instabilities in AlSi1MgMn

80%
Molnárová O., Dobroň P., Chmelík F.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
801-804
EN
The influence of the strain rate and heat treatment on the occurrence of plastic instabilities in a cast AlSi1MgMn alloy was studied. The samples were uniaxially loaded in compression at various strain rates and at room temperature. The tests were done with concurrent acoustic emission monitoring and the acoustic emission parameters are correlated to the microstructure and to the stress-strain curves in order to better understand the patterns of plastic deformation. All samples exhibited the Portevin-Le Chatelier effect of different types, dependently on the heat treatment and the applied strain rate. The occurrence of the Portevin-Le Chatelier effect is manifested by acoustic emission signals with high amplitudes. Statistical analysis of the acoustic emission signals shows the power-law probability distribution.
11
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Acoustic-Emission Study of Intermittency of Plastic Flow during Twinning and Dislocation Glide

80%
Shashkov I., Lebedkina T., Lebyodkin M., Dobron P., Chmelik F., Kral R., Parfenenko K., Mathis K.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
430-434
EN
Recent studies of plastic deformation with the aid of acoustic emission techniques proved an intermittent, scale-invariant character of plastic processes, as reflected in power-law statistical distributions. In some cases, the power-law exponents display close values leading to hypothesis of universality of scaling laws for various mechanisms of plasticity. Nevertheless, the accurate determination of the power law may be impeded by some sources of errors inevitable in real conditions, in particular, by superposition of individual acoustic emission events. In the present work, the sensitivity of the apparent statistics to the variation of the parameters of individualization of acoustic emission events is examined using Mg and Al based alloys. Both these alloys exhibit a highly cooperative character of plastic deformation, leading to strong acoustic activity which is governed by distinct microscopic mechanisms - mechanical twinning and the Portevin-Le Chatelier effect, respectively.
12
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Crystal Plasticity Treated as a Quasi-Static Material Flow through Adjustable Crystal Lattice

80%
Kratochvíl J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
482-484
EN
Considering high pressure torsion experiments as a motivation, plastic behavior of crystalline solids is treated as a highly viscous material flow through an adjustable crystal lattice. Instead of the traditional decomposition rule considering the deformation gradient as a product of the elastic and plastic parts, the proposed model is based on its rate form: the velocity gradient consists of the lattice velocity gradient and the sum of the velocity gradients corresponding to the slip rates of individual slip systems; the slip strains themselves are not defined in the model. The geometrical changes caused by material flow and the slip strains can be specified a posteriori. Crystal lattice distortions are measured with respect to a lattice reference configuration. In an adopted rigid plastic approximation the lattice distortions are reduced to rotations. Constitutive equations incorporate non-local hardening caused by close range interactions among dislocations.
13
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Creep Deformation of Intermetallic TiAl-Based Alloy

80%
Lapin J., Staneková H.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
453-456
EN
In the present work, the creep deformation behaviour of a new cast intermetallic Ti-46Al-8Ta [at.%] alloy is analysed. Constant load tensile creep tests were performed at initial applied stresses ranging from 200 to 400 MPa in the temperature range from 973 to 1073 K. The measured creep deformation curves are analysed and the observed deviations from calculated curves are discussed based on microstructural changes observed in the studied alloy during creep. The kinetics of creep deformation are evaluated in terms of the true activation energy for creep and the stress exponent. Creep damage initiation and propagation leading to the fracture of the creep specimens are characterized as functions of the applied stress and temperature.
14
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Effect of Temperature on Grain Refinement of Mg-3Al-1Zn Alloy Processed by Equal Channel Angular Pressing

80%
Molnár P., Jäger A., Lejček P.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
461-464
EN
In this work the effect of temperature on grain refinement of Mg-3Al-1Zn alloy (AZ31B) processed by equal channel angular pressing using route A is described. The deformation sequences consisted of equal channel angular pressing passes at 200C followed by passes at 150°C. Nonhomogeneous grain size distribution promotes shear band formation at 150°C. Shear bands with microcracks inside were analyzed by electron backscatter diffraction technique.
15
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Intermittency and Deformation Band Propagation in an Austenitic FeMnC TWIP Steel

80%
Lebyodkin M., Lebedkina T., Roth A., Allain S.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
478-481
EN
Plastic deformation of austenitic FeMnC TWIP steels exhibits complex spatiotemporal patterns associated with the occurrence of deformation bands and the concomitant fluctuations of the deforming stress. Although the plastic instability is a generic property of these steels and is usually attributed to interaction of dislocations with solutes (the Portevin-Le Chatelier effect), both the kinematics of the deformation bands and the characteristic shape of stress serrations observed in the carbon-containing TWIP steel at room temperature manifest unusual features. The nature of these peculiarities and the mechanism of jerky flow in such steels are unclear. In the present work, an attempt is made to get an insight into the jerky flow in the Fe22Mn0.6C steel by studying the time series characterizing the evolution of plastic deformation at various scales: stress-time curves, local strain field, and acoustic emission accompanying the deformation processes. Stress and strain fluctuations related to two distinct scale ranges are detected and characterized.
16
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Evolution of Matrix-Twin Interfaces of (101̅2) Twin in Magnesium

80%
Ostapovets A., Serra A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
661-663
EN
Recently, the presence of basal-prismatic interfaces in hexagonal close packed metals became subject of intensive investigation. We model the {101̅2} twin in magnesium bounded by two types of boundaries, i.e. {101̅2} interface and basal-prismatic facets. The migration of all boundary types is mediated by the motion of interfacial disconnections. It was shown that basal-prismatic interfaces play an important role in twin growth. The lengths of basal-prismatic facets remain constant during migration independently of the applied strain. In contrast, the {101̅2} interfaces increase their lengths during growth.
17
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Phase Analysis of NiTi Shape Memory Wires and Computer Simulations of the Superelastic Effect

80%
Młocek B., Lekston Z., Zubko M., Rak J., Stróż K.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1063-1065
EN
Shape memory alloys belong to the group of intelligent materials due to their exceptional properties related to reversible martensitic transformation. They show both superelasticity and shape memory effects. The modelling of the superelastic phenomena occurring in NiTi alloys is important due to its application in the further development of materials for dedicated applications. A computer simulation of static tensile test was carried out using the finite element method for NiTi wire and obtained results were compared with experimental curve. For the determination of phase composition at ambient temperature and courses of phase transitions during cooling and heating the X-ray powder diffraction and differential scanning calorimetry methods were used. X-ray diffraction phase analysis exhibited that the studied wire at room temperature has B2 - parent phase structure. Additionally, differential scanning calorimetry measurements showed that the phase transformations during cooling and heating occur in a temperature range of about -20 to +30°C.
18
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AFM Observation of Fe-Al Single Crystals under in situ Deformation

80%
Veselý J., Cieslar M., Kopeček J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
618-621
EN
Fe-Al single crystals of three different compositions (20, 28 and 40 at.% Al) in single slip orientation were studied. Evolution of their surfaces during deformation at room temperature was observed in situ in atomic force microscope. Atomic force microscopy allows us to investigate slip lines on much finer scale than traditional optical observations. Wavy slip bands in Fe-Al_{20}, cross-slip in Fe-Al_{28} and weak slip line texture in Fe-Al_{40} are described. Post mortem observations of surfaces of Fe-Al_{28} deformed at elevated temperatures (in the range of yield stress anomaly) are presented as well.
19
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The Study of the Behavior of Constrained Groove Pressed Magnesium Alloy after Heat Treatment

80%
Zimina M., Bohlen J., Letzig D., Kurz G., Poková M., Knapek M., Zrník J., Cieslar M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
775-778
EN
In this work twin-roll cast AZ31 magnesium strip of thickness 5.6 mm was subjected to the heat treatment and further constrained groove pressing. A comparison of the microstructure and microhardness of as-cast, constrained groove pressed and annealed material was carried out. The twin-roll cast strip exhibits an inhomogeneous structure which is replaced by a finer and uniform recrystallized one after aging at 450°C for 10 h. A significant increase of the microhardness was observed accompanied by a pronounce grain refinement. Nevertheless, the distribution of the grain size is unequal along the specimen width. Thermal stability of the deformed structure during subsequent annealing was investigated. It was shown that higher annealing temperatures result in a formation of a more uniform recrystallized structure and in a significant drop of microhardness down to the values obtained for as-cast alloy.
20
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Heat Treatment of CuFe2 and CuCr0.6 Alloys and the Effect of Precipitates on the Grain Refinement

71%
Urbańczyk-Gucwa A., Amrogowicz P., Jabłońska M., Rodak K.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1016-1019
EN
The results of microstructure and hardness investigations of the CuFe2 and CuCr0.6 alloys after solution and ageing treatment are presented in this paper. The variants of heat treatment as: solution at 1000°C per 3 h and ageing treatment at 500°C for 2 h and at 700°C for 24 h were chosen for severe plastic deformation process realized by rolling with the cyclic movement of rolls method. The structure of CuFe2 and CuCr0.6 alloys was analysed using scanning transmission electron microscopy, and the quantitative studies of the substructure was performed with MET-ILO software, on the basis of images acquired on scanning transmission electron microscope.
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