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1

A new crystal plasticity model incorporating precipitation strengthening to simulate tensile deformation behavior of AA2024 alloy

Singh Lakhwinder, Ha Sangyul, Vohra Sanjay, Sharma Manu

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e155, 2023

EN

In this work, a constitutive model is developed by incorporating precipitation strengthening into a dislocation-density-based crystal plasticity (CP) model to simulate the mechanical properties of 2024 aluminium alloy (AA). The proposed model considers the contributions of solid solution strengthening and strengthening from dislocation–precipitate interactions into the total slip resistance along with the forest hardening due to dislocation–dislocation interactions. A term accounting for the multiplication of dislocations due to their interactions with the non-shearable precipitates in the alloy is incorporated in the hardening law. The developed precipitation strengthening-based CP model is implemented into the crystal plasticity finite element method (CPFEM) for simulating the macroscopic mechanical behavior of AA2024-T3 alloy for uniaxial tension over various strain rates. The macroscopic response of the polycrystal representative volume element (RVE) used for simulations is computed using computational homogenization. The effect of meshing resolution on the RVE response is studied using four different mesh discretizations. Predictions of the macroscopic behavior by the developed model are in good agreement with the experimental findings. Additionally, the contribution of model parameters to the total uncertainty of the predicted stress has been assessed by conducting a sensitivity analysis. A parametric analysis with different precipitate radii and volume fractions has been done for finding the effect of precipitates on the macroscopic and localized deformation.

2

Misfit dislocation in a precipitate/matrix interface of any orientation relative to the matrix free-surface

Colin J.

Archives of Mechanics

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2020

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Vol. 72, nr 5

445--464

EN

The presence of an edge dislocation in a surface of a two-dimensional precipitate of square shape embedded in a semi-infinite matrix has been discussed when the precipitate is submitted to misfit strain due to the lattice mismatch between the two phases. Considering any orientation of the precipitate relative to the matrix free-surface, the total force applying on the dislocation has been analytically calculated and its equilibrium position has been determined. The conjugated effects of the precipitate misorientation, of the lattice mismatch and of the precipitate/matrix distance have been finally characterized. A shifting effect on this equilibrium position has been analyzed.

3

Microhardness analysis of halite from different salt-bearing formations

Toboła Tomasz Tadeusz, Cyran Katarzyna, Rembiś Marek

Geological Quarterly

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2019

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Vol. 63, No. 4

771--785

EN

Microhardness tests were carried out on single halite crystals. They were conducted on the (001) surface, with the indenter set in two directions: parallel to the halite face (010); and parallel to the (110) face. The halite crystals represent salt formations of different ages (Devonian, Zechstein, Badenian), depths (from 1835.5 to 195 m) and intensities of tectonic disturbance (horizontally stratified, salt dome, strongly folded). The measurement results revealed specific features of the halite crystals analysed. Firstly, the data obtained show microhardness anisotropy in halite crystals. Moreover, microhardness correlates with the depth of the salt-bearing formations. Halite crystals from deeper levels showed higher microhardness, though there was no correlation between the intensity of tectonic deformation and the average Vickers hardness (HV). The samples analysed show a variability of HV values and and of the shapes of imprints. These indicate zones where halite crystals are deformed at the atomic level and reflects the presence of defects in the crystal lattice. Such deformation is reflected in an irregularity of the strike of cleavage planes. Consequently, the analysis of imprint shapes is a useful method for the examination of ductile minerals and materials.

4

Oxide crystals on the surface of porous indium phosphide

Suchikova Y. O., Bogdanov I. T., Kovachov S. S.

Archives of Materials Science and Engineering

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2019

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Vol. 98, nr 2

49--56

EN

Purpose: f this paper is to is to establish the patterns of oxide formation on the surface of indium phosphide during electrochemical etching of mono-InP. Design/methodology/approach: A porous surface was formed with the anode electrolytic etching. Morphology of the surface was studied with the help of scanning electron microscope JSM-6490. The analysis of chemical composition of porous surface of samples was also performed. Findings: It was shown that during the electrochemical etching of indium phosphide, oxide films and crystallites form on the surface. It has been established that crystalline oxides are formed mainly on the surface of n-type indium phosphide. Continuous oxide films are predominantly formed on the surface of p-InP. Research limitations/implications: The research was carried out for indium phosphide samples synthesized in the solution of hydrofluoric acid, though, carrying out of similar experiments for crystalline oxides on the surface of porous indium phosphide obtained in other conditions, is necessary. Practical implications: The study of oxide crystals on the surface of porous indium phosphide has great practical importance since it is the reproducibility of experimental results that is the main problem of modern materials science, the more nanoengineering. Oxides can significantly affect the properties of materials. On the one hand, oxides significantly affect the recombination properties of materials, this can impair the operation of semiconductor devices. On the other hand, oxide films can serve as a passivating coating for the surface of a porous semiconductor. Such an oxide property will be useful for the practical application of nanostructured indium phosphide. Therefore, questions of the conditions for the formation of semiconductor intrinsic oxides, their structure, and chemical composition, and also the effect of oxides on the physical and technical characteristics of materials are important. Originality/value: The patterns of oxide formation on the surface of indium phosphide during electrochemical etching are investigated in this work. It is shown for the first time that the structure of an oxide depends on the orientation of the surface of the semiconductor. It was shown that continuous oxide films are formed on the surface of p-InP, and oxide crystalline clusters are formed on the surface of n-InP.

5

Radiation-stimulated changes in the characteristics of surface-barrier AL–SI–BI structures with different concentrations of dislocations at the crystal surface

Pavlyk B., Kushlyk M., Slobodzyan D., Matvijishyn I., Lys R., Jałbrzykowski M.

Acta Mechanica et Automatica

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2018

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Vol. 12, no. 1

72--77

EN

We report the results of studies for the radiation-stimulated changes in electro-physical characteristics of surface-barrier Al–Si–Bi structures based on p-Si. We demonstrate that the X-ray irradiation is accompanied by different processes which depend on the density of the dislocations in the original silicon crystals. A usual evolution of the existing structural defects and their radiationstimulated ordering dominate when the concentration remains low enough. Increase in the concentration causes the increasing role of generation of additional radiation defects. Modelling of the underlying physical processes has testified that the near-contact Si layers are strained. They act as getters for the structural defects and impurities.

6

The influence of temperature and strain rate on the strengthening of metallic materials

Kyzioł L.

Journal of KONES

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2016

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Vol. 23, No. 1

199--206

EN

Extensive literature indicates that the effect of strengthening materials is related to their structural construction. The structure of the metallic material exhibits the greatest strengthening effect when there is a very limited movement of dislocations and their movement is completely blocked due to numerous obstacles [1, 3, 6-9, 12, 15, 16]. In this paper strain, rate and temperature dependences of yield strength of metallic materials are presented. The effect of temperature and strain rate on the value mechanical threshold stress is determined. In addition, the effect of temperature on the Kirchhoff modulus and Burgers vector is determined. The interaction of dislocations with grain boundaries causes additional stress – athermal stress causing the strengthening of the structure. The term “athermal” implies that thermal activation is unable to assist the dislocation past these obstacles. The strengthening of metallic materials is related to the dimensions of the grains, which influence the athermic stress. The calculations of mechanical threshold stress and other parameters of the structure of the material allow for easier understanding of the strengthening of the material loaded with temperature and strain rate. The largest strengthening occurs in pure metals and their alloys in the case of the total blocking of dislocation motion. This process takes place when the temperature is 0 K or at very high strain rates. The metal demonstrates the greatest effort, which is called mechanical threshold stress (MTS) [5].

7

Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method

Pawełek A., Piątkowski A., Wajda W., Skuza W., Tarasek A., Ranachowski Z., Ranachowski P., Ozgowicz W., Kúdela Jr., Kúdela S.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 2A

897--904

EN

The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al and Mg4Li4Zn alloys subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloys and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the relation between plastic flow instabilities and the fracture characteristics. There are discussed the possible influence of the factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries, interaction of solute atoms with mobile dislocations (Cottrell atmospheres) as well as dislocation pile-ups which may lead to the microcracks formation due to the creation of very high stress concentration at grain boundaries. The results show that the plastic flow discontinuities are related to the Portevin-Le Châtelier phenomenon (PL effect) and they are correlated with the generation of characteristic AE pulse trains. The fractography of broken samples was analyzed on the basis of light (optical), TEM and SEM images.

8

Stan naprężenia i wytężenia górotworu w otoczeniu struktur elewacyjnych LGOM – w świetle wyników modelowania numerycznego

Chlebowski D., Kowol W.

Przegląd Górniczy

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2013

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T. 69, nr 5

65--72

PL

W artykule przedstawiono numeryczną ocenę kształtowania się stanu naprężenia górotworu w sąsiedztwie charakterystycznych dla rejonu LGOM zaburzeń geologicznych typu elewacyjnego w aspekcie lokalizacji obszarów możliwego naruszenia pierwotnej ciągłości struktury ośrodka skalnego. Identyfikacja takich stref ma istotne znaczenie z punktu widzenia warunków sprzyjających występowaniu skutków wysokoenergetycznej sejsmiczności górotworu, a z racji powstałej zwiększonej szczelinowatości również zjawisk wyrzutów gazów i skał. Próbę opisu zagadnienia modelowego podjęto z wykorzystaniem opartego na metodzie elementów skończonych oprogramowania numerycznego Cosmos/M, natomiast dla realizacji celów merytorycznych przytoczono i omówiono mapy warstwicowe zmienności współczynników koncentracji (składowej pionowej i poziomej) przestrzennego stanu naprężenia oraz wskaźnika wytężenia górotworu dla wytypowanych wariantów zmian miąższości warstwy złożowej w otoczeniu zaburzenia.

EN

This article presents a numerical assessment of stress forming in the rock mass adjacent to the elevation dislocations, typical of the LGOM area, in respect of areas with possible disturbance of primary continuity of the rock center. The identification of such zones is crucial for the favouring conditions of high-energy rock mass seismic activity effects occurrence. Because of the increased fissuring it also relates to the gas rock outburst and squealers. The attempt to describe the modeling issue was taken by use of the numerical software Cosmos/M based on the finite element method. Alternatively, for the content-related purposes, the issues of contour map of the fluctuations of stress spatial differential absorption ratios (vertical and horizontal component) and rock mass effort index for the indicated options of the strata thickness changes in the surroundings of the dislocation were discussed.

9

Recognition and characterization of defects in GaN epilayers

Jezierska E., Borysiuk J.

Inżynieria Materiałowa

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2013

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Vol. 34, nr 4

277--282

EN

Using conventional and high resolution electron microscopy typical contrast was identiﬁed for the “a” pure edge threading dislocations in GaN layers grown on SiC and sapphire. Their atomic structure was shown to exhibit 5/7 atoms conﬁguration. The {1 2 10} stacking fault has two atomic conﬁgurations in wurtzite GaN with 1/2<10 1 1> and 1/6<20 2 3> displacement vectors. It originates from steps at SiC surface and it can form on a flat (0001) sapphire surface. In the investigated samples mainly Holt conﬁguration of inversion domains and zigzag boundaries were found. This conﬁguration is realized by inversion with displacement c/2. Different types of nanopipes were found on the cross-sectional GaN/Al2O3 specimens. Most of the observed nanopipes have hexagonal cross-section on planar view and the diameter in the range 5÷20 nm. Screw distortion around the nanopipes was conﬁrmed using Large-Angle Convergent-Beam Electron Diffraction (LACBED) images. Cubic-GaN inclusions were found as colonies of triangular pyramids with the hill of triangle towards SiC substrate. The appearance of second phase precipitates inside wurtzite GaN epilayer is associated with stacking mismatch boundaries and misoriented mosaic domains. The size of c-GaN inclusions is in the range 2÷16 nm with average lateral diameter near 5 nm.

PL

Krawędziowe dyslokacje typu ,,a” przebiegające na wskroś warstw epitak- sjalnych GaN/SiC zidentyﬁkowano na podstawie typowego kontrastu, stosując techniki konwencjonalne i wysokorozdzielczą mikroskopię elektronową. Określono atomową konﬁgurację rdzenia dyslokacji, jako układ 5/7 najbliższych atomów. Występujące w strukturze wurcytu błędy ułożenia {1 2 10} przyjmują w badanych warstwach epitaksjalnych GaN dwie konﬁgurację 0 różnych wektorach przemieszczenia 1/2<10 1 1> i 1/6<20 2 3>. Powstają one na skutek tworzenia stopni na powierzchni podłoża SiC lub na płaskich powierzchniach bazowych szaﬁru. Stwierdzono występowanie granic domen inwersyjnych i granic typu zig-zag o konﬁguracji charakteryzującej się złożeniem inwersji i przemieszczenia c/2 w kierunku osi heksagonalnej. W warstwach epitaksjalnych GaN/szaﬁr zaobserwowano nanorurki jako dyslokacje śmbowe o otwartym rdzeniu. Większość nanorurek na przekroju planarnym wykazywała kształt heksagonahiy i rozmiary w zakresie 5 ÷20 nm. Dystorsja śmbowa wokół nanorurek została potwierdzona za pomocą metody zbieżnej wiązki elektronów przy dużych kątach zbieżności (LACBED). W strukturze heksagonalnej GaN/SiC zaobserwowano obszary fazy o sieci regulamej c-GaN, jako kolonie o kształcie odwróconych piramidek o wielkości u podstawy 2÷16 nm, przy średniej wielkości 5 nm.

10

Geometry of stress function surfaces for an asymmetric continuum

Yajima T., Yamasaki K., Nagahama H.

Acta Geophysica

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2013

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Vol. 61, no. 6

1703--1721

EN

A two-dimensional stress field of dislocation or fault is geometrically studied for an asymmetric con tinuum. For geometric surfaces of the stress and couple-stress functions, the mean and Gaussian curvatures are derived. The mean curvature of couple-stress function surface is connected with the asymmetr ic of stress tensor. Moreover, the Gaussian curvature of stress function surface is characterized by bo th the stress and couple-stress. On the other hand, th e mean curvature of stress function surface is not affected by the asy mmetry of stress. Based on these geometric expressions, the Coulomb’s failure criterion and the friction coefficient are expressed by the curvatur es of couple-stress function surface. Moreover, geometric structures of st ress and couple stress function surfaces are shown for edge and wedge dislocations as faults. The curvatures of these surfaces show that the ef fect of couple-stress is constrained around the dislocations only.

11

A novel approach to increase emission wavelength of InAs/GaAs quantum dots by using a quaternary capping layer

Chowdhury S., Adhikary S., Halder N., Chakrabarti S.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

246-249

EN

In this paper, we present a new approach to obtain large size dots in an MBE grown InAs/GaAs multilayer quantum dot system. This is achieved by adding an InAlGaAs quaternary capping layer in addition to a high growth temperature (590°C) GaAs capping layer with the view to tune the emission wavelength of these QDs towards the 1.3 µm/0.95 eV region important for communication devices. Strain driven migration of In atoms from InAlGaAs alloy to the InAs QDs effectively increases the size of QDs. Microscopic investigations were carried out to study the dot size and morphology in the different layers of the grown samples. Methods to reduce structural defects like threading dislocations in multilayer quantum dot samples are also studied.

12

TEM analysis of creep mechanisms of single-crystalline nickel-base superalloys

Dubiel B., Czyrska-Filemonowicz A.

Inżynieria Materiałowa

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2010

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Vol. 31, nr 3

610-613

EN

Microstructural changes during creep of <001> oriented single crystal Ni-base superalloys CMSX-4 and CM186LC at temperatures 750°C and 950°C have been analyzed in detail by means of transmission electron microscopy (TEM). These observations allowed the identification of the mechanisms controlling the creep deformation of single crystal superalloys with different volume fraction of y-y' eutectic. The present paper discuss in particular the following mechanisms: dislocation slip and climb in the y channels, cutting of y' precipitates by dislocation ribbons, formation of interfacial dislocation networks and morphological changes of cuboidal y' caused by rafting. Deformation of large interdenritic y' precipitates and its influence on creep strain is also discussed.

PL

Metodami transmisyjnej mikroskopii elektronowej zbadano zmiany mikrostruktury podczas pełzania monokrystalicznych nadstopów niklu CMSX-4 i CM186LC o orientacji <001> w temperaturze 750°C i 950°C. Obserwacje mikrostruktury pozwoliły na ustalenie mechanizmów kontrolujących odkształcenie podczas pełzania monokrystalicznych nadstopów niklu z rożnym udziałem eutektyki y/y'. W artykule omówiono następujące mechanizmy pełzania: poślizg (rys. 3, 4) i wspinanie dyslokacji w kanałach fazy y, przecinanie wydzieleń y' przez wstęgi dyslokacyjne (rys. 5), tworzenie siatek dyslokacyjnych na granicach międzyfazowych y/y' (rys. 7), zmiany kształtu sześciennych wydzieleń y' wskutek raftingu (rys. 8, 9). Zaobserwowano także odkształcenie dużych wydzieleń y' w obszarach międzydendrytycznych (rys. 6).

13

Badanie warunków procesów trawienia i polerowania mechaniczno-chemicznego podłoża GaSb o orientacjach [100] i [111]

Bańkowska A., Mirowska A., Pawłowska M.

Elektronika : konstrukcje, technologie, zastosowania

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2010

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Vol. 51, nr 1

50-52

PL

Zbadano wpływ roztworów trawiących i polerskich na stan powierzchni płytek GaSb o orientacjach [100] i [111]. Wykonano próby polerowania, które dały pozytywne rezultaty. Uzyskano powierzchnię, której chropowatość wynosiła mniej niż 5Å. Zostały także przeprowadzone testy osadzenia warstwy epitaksjalnej na podłoża, które potwierdziły poprawny dobór mieszanin polerskich i warunków polerowania.

EN

The influence of etching and polishing solutions on GaSb surface have been investigated. The applied polishing procedures gave positive resultes. Roughness of wafers surface was less than 5Å. The epitaxial test confirmed high quality of the GaSb substrates.

14

Reducing the density of threading dislocations in GaAs epitaxial layers. Efficiency assessment of isovalent Bi doping and Pb doping

Baganov Y. E., Krasnov V., Lebed O., Lebed O., Shutov S.

Materials Science Poland

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2009

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Vol. 27, No. 2

355--363

EN

Processes of motion of threading dislocations associated with isovalent doping of epitaxial layers were considered. An exact solution was obtained for the gliding distance of dislocations under strains. It was shown that the effectiveness of doping for reducing the density of threading dislocations in an epitaxial layer depends on the product of the surface density of the dislocations in the substrate and the lateral size of the substrate. An analysis of the effectiveness of isovalent Bi doping and standard Pb doping in reducing the density of threading dislocations in GaAs epitaxial layers and the range of applicability has been presented.

15

Twinning and shear band formation in channel-die compressed silver single crystals identified by acoustic emission method

Jasieński Z., Pawełek A., Piątkowski A., Ranachowski Z.

Archives of Metallurgy and Materials

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2009

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Vol. 54, iss. 1

29-33

EN

In the paper there are presented the results of investigations of the relations between acoustic emission (AE) and the mechanisms of twinning as well as shear band formation and propagation in silver single crystals of {112}<111> orientation, subjected to channel-die compression tests at ambient temperature. The results were obtained using an AE analyzer of a new generation, installed recently at the Institute of Metallurgy and Materials Science, and were compared with those obtained also for single Ag crystals of the same orientation, tested at the room and at liquid nitrogen (-196°C) temperatures, but registered applying an AE analyzer of older generation, used until now. The results of AE measurements obtained using the new analyzer allowed to plot the acoustograms obtained with the application of Windowed Fast Fourier Transform (FFT) method for analysis of large experimental data sets (4 X 132 Msamples). This allowed the authors to attack the problem of identification of the strain mechanisms leading to formation of different dislocation systems.

PL

W artykule zaprezentowano zależność pomiędzy natężeniem generowanego sygnału emisji akustycznej (EA), a mechanizmami bliźniakowania i tworzenia oraz rozwoju pasm ścinania w monokryształach srebra o orientacji {112}<111>, poddanych nieswobodnemu ściskaniu w komorze kanalikowej w temperaturze otoczenia. Badania prowadzono przy pomocy analizatora EA nowej generacji zainstalowanego w Instytucie Metalurgii i Inżynierii Materiałowej PAN. Otrzymane rezultaty porównano z wynikami testów ściskania monokryształów srebra o tej samej orientacji prowadzonych przy temperaturze pokojowej oraz przy temperaturze cieklego azotu (-196°C) przy zastosowaniu analizatora EA starszej generacji. Wyniki badan nowszym analizatorem zostały przedstawione w postaci akustogramów uzyskanych za pomocą algorytmu Okienkowej Szybkiej Transformaty Fouriera, zaprojektowanego do obróbki obszernych zbiorów danych eksperymentalnych (4x132x10do 6 próbkowań). Zastosowanie metody akustogramów pozwoliło autorom artykułu na identyfikacje mechanizmów odkształcenia w badanym materiale, prowadzących do uformowania sie różnych systemów dyslokacji.

16

Computer simulation of magnetoplasticity dislocation motion in magnetic and stress fields

Alshits V., Kotowski R., Tronczyk P.

Przegląd Elektrotechniczny

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2007

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R. 83, nr 7-8

89-92

EN

The magnetoplasticity effect (MPE) was discovered in 1985 at the Institute of Crystallography in Moscow, Russia. It was checked many times in different materials, confirmed in independent laboratories and described in a number of papers. The experimental studies were conducted on the samples of the alkali compounds, nonmagnetic metals and semiconductors. The results of the computer simulations of the effect are presented.

PL

Zjawisko magnetoplastyczności (M)E zostało odkryte w roku 1985 w Instytucie Krystalografii w Moskwie, Rosja. Zostało ono stwierdzone wielokrotnie w różnych materiałach i potwierdzone licznymi publikacjami niezależnych grup badawczych. Prace doświadczalne prowadzono z próbkami związków alkalicznych, metali niemagnetycznych i półprzewodników. Tu przedstawiono wyniki komputerowych symulacji MPE.

17

<100> burgers vector dislocations inherited by second overshoot FCC twinning

Szczerba M. S., Tokarski T., Perek M.

Archives of Metallurgy and Materials

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2007

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Vol. 52, iss. 2

193-201

EN

TEM observations of <100> Burgers vector dislocations in twinned copper-aluminum alloy single crystals are reported. It is found that network of cube dislocations result from a growing twin and conjugate slip interactions which originate at the end of the second overshoot of the tensile deformation of low stacking fault energy FCC crystals. It is also found that the dislocation network of the cube dislocations is usually accompanied with another network of extrinsic Frank dislocations resulting from a dissociation of cube dislocation segments attached to the twin shear plane. The experimental results obtained in this paper fully support those reported in the paper by Basinski et al. [1], which showed that the cube dislocations may also result from a growing twin and primary slip interactions associated with the first overshoot FCC twinning.

PL

W pracy przedstawione są obserwacje elektronomikroskopowe dyslokacji o wektorze Burgersa <100> w monokryształach miedź-aluminium, które uległy bliźniakowaniu. Pokazano, że sieć dyslokacji kubicznych powstaje w skutek interakcji między powstającym bliźniakiem a dyslokacjami poślizgu sprzężonego, która rozpoczyna się z końcem II overshootu podczas rozciągania kryształów RSC o niskiej energii błędu ułożenia. Wykazano również, że sieci dyslokacji kubicznych zwykle towarzyszy sieć dyslokacji Franka stowarzyszonych z zewnętrznymi błędami ułożenia, które powstają z dysocjacji segmentów dyslokacji kubicznych przytwierdzonych do płaszczyzny ścięcia bliźniaczego. Wyniki eksperymentalne otrzymane w pracy potwierdzają te przedstawione w pracy Basińskiego i in. [1], w której pokazano, że dyslokacje kubiczne moga również powstawać w wyniku interakcji między powstającym bliźniakiem a dyslokacjami poślizgu pierwotnego towarzyszącej zjawisku I overshootowi podczas bliźniakowania w kryształach o sieci RSC.

18

Acoustic emission and the Portevin-Le Châtelier effect in tensile tested Al alloys processed by ARB technique

Pawełek A., Kuśnierz J., Bogucka J., Jasieński Z., Ranachowski Z., Ranachowski P., Rejmund F., Dębowski T.

Archives of Acoustics

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2007

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Vol. 32, No. 4

955--962

EN

The paper presents the investigations of the relation between the acoustic emission (AE) and the Portevin-Le Châtelier (PL) phenomena occurring in tensile tested two kinds of aluminium alloys: not-predeformed and predeformed earlier using the technique of accumulative rolling banding (ARB). There have been found essential correlations between AE and PL effects in ARB not-predeformed alloys. The tensile tests for ARB predeformed alloys were performed on a series of samples of various degree of work hardening and it has been observed that the correlations between the AE and PL effects are not so pronounced as in the case of ARB not-predeformed alloys. The results of AE measurements obtained using a new software allowed additionally to carry out the spectral analysis of AE signals and, in consequence, to determine the acoustic maps (acoustograms) and the spectral characteristics which are very useful in the discussion of the relations between the non-homogeneous strain mechanisms of the PL effect and the mechanisms of AE events generation. The results are discussed in the context of the existing dislocation models of the PL effect and the theoretical concepts of AE sources.

19

Characterization of the structure of FeAl alloy after hot deformation

Jabłońska M., Rodak K., Niewielski G.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

107--110

EN

Purpose: Purpose of this paper was the study of the microstructure of Fe-38Al alloy after hot deformation with the dislocation structure description. Design/methodology/approach: Methodology of the microstructures research included LM (light microscopy) and TEM (transmission electron microscopy) techniques which has characterized the dislocation structure in these materials. The Fe-38Al alloy has been deformed by torsion plastometer within the range of temperatures from 850°C to 1250°C. All samples has been deformed to rupture. Findings: The findings of this study is that the deformation in this alloy is controlled by dislocation motion. The observed dislocations are predominantly of <100> and <111>. At a deformation temperature of 1100°C TEM observations have shown dislocation loops and helices. In this alloy was observed dynamic recrystalization process during the hot deformation. Practical implications: Practical implications of this research is that this alloy may by deformed in long range of strain in temperatures at 800°C to 1000°C Occure 1100°C the plasticity is limited by order - disorder transformation. This transformation could be responsible for dislocations structure behavior what was found. Originality/value: Value of this paper was important in providing a better understanding of technological plasticity of FeAl alloys. The dislocation and reactions between the defects of the structure play a dominant role and are responsible for the variation of technological plasticity.

20

Przemieszczenia maszyn podstawowych pomiędzy odkrywkami w KWB "Konin"

Kasztelewicz Z., Czyż J., Czaplicki P., Jagodziński Z.

Górnictwo Odkrywkowe

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2006

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R. 48, nr 3-4

116-120

PL

W artykule przedstawiono sposoby przemieszczeń maszyn podstawowych między odkrywkami stosowane w wieloodkrywkowej kopalni węgla brunatnego "Konin". Przedstawiono przebiegi wybranych przemieszczeń. Opisano korzyści techniczne, ekonomiczne i czasowe wynikające z przemieszczania maszyn na własnym podwoziu.

EN

This paper presents the methods of basic machines dislocation between open pits applied in Konin multi-level lignite mine. A course of selected dislocation has been presented. Technological and economic advantages resulting from machines dislocation have been described.