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1

Effect of milling time on microstructure of cobalt ferrites synthesized by mechanical alloying

Tomiczek Anna E.

Archives of Materials Science and Engineering

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2021

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Vol. 111, nr 1

5--13

EN

Purpose: of this paper is to determine the effect of manufacturing conditions, especially milling time, on the microstructure and phase composition of CoFe2O4 cobalt ferrite. Design/methodology/approach: Cobalt ferrite (CoFe2O4) has been synthesised from a stoichiometric mixture of CoCo3 and α-Fe2O3 powders in a high energy planetary mill. Annealing at 1000°C for 6 hours after milling was used to improve the solid-state reaction. Calcinated samples were analysed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The relationship between the milling time of powders, their microstructure, as well as their properties were evaluated. Particles size distribution and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) examination were also made. Findings: CoFe2O4 ferrites were successfully synthesized by mechanical alloying of α-Fe2O3 and CoCO3 powders. The powder particles had undergone morphological changes with the increasing milling time. However, the milling time does not affect the ferrite formation rate. It is expected that the improvement of fabrication parameters can further enhance the properties of cobalt ferrite presented in this work. Research limitations/implications: Contribute to research on the structure and properties of cobalt ferrites manufactured by mechanical alloying. Practical implications: The reactive milling and subsequently annealing is an efficient route to synthesise cobalt ferrite powder. However, using steel milling equipment risks powder contamination with iron and chromium from the vials and balls. Originality/value: The results of the experimental research of the developed ferrite materials served as the basis for determining material properties and for further investigation.

2

Towards cubic modification of Li7La3Zr2O12 compound by mechanical milling and annealing of powders

Oleszak D., Kurowski B., Pikula T., Pawlyta M., Senna M., Suzuki H.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 1

13--16

EN

The aim of these studies was to obtain single phase cubic modification of Li7La3Zr2O12 by mechanical milling and annealing of La(OH)3, Li2CO3 and ZrO2 powder mixture. Fritsch P5 planetary ball mill, Rigaku MiniFlex II X-ray diffractometer, Setaram TG-DSC 1500 analyser and FEI Titan 80-300 transmission electron microscope were used for sample preparation and investigations. The applied milling and annealing parameters allowed to obtain the significant contribution of c-Li7La3Zr2O12 in the sample structure, reaching 90%. Thermal measurements revealed more complex reactions requiring further studies.

3

The Influence of the Dispersion Method on the Microstructure and Properties of MWCNTs/AA6061 Composites

Dobrzański L. A., Macek M., Tomiczek B., Nuckowski P. M., Nowak A. J.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 2B

1229--1234

EN

The aim of this work was to study the effect of different methods of multi-walled carbon nanotubes (MWCNTs) dispersion, and their influence on the microstructure and properties of aluminium alloy matrix composites produced using the powder metallurgy techniques, such as powder milling/mixing and hot extrusion. The main problem in the manufacturing of nanocomposites is the homogeneous distribution of MWCNTs in the metal matrix. To achieve their proper distribution a high-energy and low-energy mechanical milling, using a planetary ball mill, and mixing, using a turbulent mixer, were applied. Studies have shown that composite materials prepared using milling and extrusion have a much better dispersion of the reinforcing phase, which leads to better mechanical properties of the obtained rods. The low-energy mechanical mixing and mixing using the turbulent mixer neither change the powder morphology nor lead to adequate dispersion of the carbon nanotubes, which directly affects the resulting properties.

4

Effect Of Milling Time On Microstructure Of AA6061 Composites Fabricated Via Mechanical Alloying

Tomiczek B., Pawlyta M., Adamiak M., Dobrzański L. A.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

789--793

EN

The aim of this work is to determine the effect of manufacturing conditions, especially milling time, on the microstructure and crystallite size of a newly developed nanostructural composite material with the aluminium alloy matrix reinforced with halloysite nanotubes. Halloysite, being a clayey mineral of volcanic origin, is characterized by high porosity and large specific surface area. Thus it can be used as an alternative reinforcement in metal matrix composite materials. In order to obtain this goal, composite powders with fine microstructures were fabricated using high-energy mechanical alloying, cold compacting and hot extrusion techniques. The obtained composite powders of aluminium alloy reinforced with 5, 10 and 15 wt% of halloysite nanotubes were characterized with SEM, TEM and XRD analysis. It has been proven that the use of mechanical alloying leads to a high degree of deformation, which, coupled with a decreased grain size below 100 nm and the dispersion of the refined reinforcing particles–reinforces the material very well.

PL

Celem niniejszej pracy było określenie wpływu warunków wytwarzania, w szczególności czasu mielenia, na strukturę i wielkość krystalitów nowo opracowanych nanostrukturalnych materiałów kompozytowych o osnowie stopów aluminium wzmacnianych nanorurkami haloizytowymi. Haloizyt, będący minerałem ilastym pochodzenia wulkanicznego, charakteryzuje się dużą porowatością, dużą powierzchnią właściwą, i może stanowić alternatywne wzmocnienie metalowych materiałów kompozytowych. W tym celu przy użyciu wysokoenergetycznego mechanicznego stopowania w młynie kulowym wytworzono rozdrobnione i trwale połączone proszki kompozytowe, które następnie poddano zagęszczaniu na zimno i wyciskaniu na gorąco. Tak opracowane materiały kompozytowe o udziale masowym haloizytowego wzmocnienia 5, 10, 15% zbadano metodami skaningowej i transmisyjnej mikroskopii elektronowej oraz rentgenowskiej analizy fazowej. Stwierdzono, że wywołane mechanicznym stopowaniem silne odkształcenie plastyczne i zmniejszenie rozmiaru ziarna poniżej 100 nm oraz dyspersja haloizytowych cząstek wzmacniających wpłynęła na znaczne umocnienie materiałów kompozytowych.

5

Effect of Milling Time on Microstructure and Properties of AA6061/MWCNTS Composite Powders

Tomiczek B., Dobrzański L. A., Macek M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 4

3029--3034

EN

The main purpose of this work is to determine the effect of milling time on microstructure as well as technological properties of aluminium matrix nanocomposites reinforced with multi-walled carbon nanotubes (MWCNTs) using powder metallurgy techniques, including mechanical alloying. The main problem of the study is the agglomeration and uneven distribution of carbon nanotubes in the matrix material and interface reactivity also. In order to reach uniform dispersion of carbon nanotubes in aluminium alloy matrix, 5÷20 h of mechanical milling in the planetary mill was used. It was found that the mechanical milling process has a strong influence on the characteristics of powders, by changing the globular morphology of as-received powder during mechanical milling process to flattened one, due to particle plastic deformation followed by cold welding and fracturing of deformed and hardened enough particles, which allows to obtain equiaxial particles again. The obtained composites are characterised by the structure of evenly distributed, disperse reinforcing particles in fine grain matrix of AA6061, facilitate the obtainment of higher values of mechanical properties, compared to the initial alloy. On the basis of micro-hardness, analysis has found that a small addition of carbon nanotubes increases nanocomposite hardness.

PL

Głównym celem podejmowanej pracy było określenie wpływu czasu mechanicznego mielenia na strukturę oraz własności technologiczne nanokompozytów o osnowie stopu aluminium 6061 wzmocnionych wielościennymi nanorurkami węglowymi (MWCNTs, ang. multi-walled carbon nanotubes) z wykorzystaniem technik metalurgii proszków, w tym mechanicznej syntezy oraz wyciskania na gorąco. Głównymi problemami podjętymi w badaniach były: aglomeracja i nierównomierny rozkład nanorurek węglowych w osnowie, a także reaktywność na granicy faz. W celu uzyskania jednorodnego rozmieszczenia nanorurek węglowych w osnowie stopu aluminium zastosowano wysokoenergetyczne mechaniczne mielenie w młynie planetarnym przez 5÷20 godzin. Stwierdzono, że zmiana czasu trwania procesu mechanicznej syntezy wpływa znacząco na morfologię materiałów proszkowych, umożliwiając uzyskanie zmiany ich morfologii ze sferycznej – charakterystycznej dla stanu wyjściowego – w odkształconą plastycznie (płatkową), następnie w powtarzających się procesach zgrzewania i pękania materiału umocnionego ponownie przyjmuje postać cząstek równoosiowych. Otrzymane w procesie mechanicznej syntezy materiały kompozytowe charakteryzują się strukturą równomiernie rozłożonych, rozdrobnionych cząstek fazy wzmacniającej, w drobnoziarnistej osnowie stopu AA6061, sprzyjających osiąganiu wyższych wartości własności wytrzymałościowych w porównaniu do stopu wyjściowego. Na podstawie badań mikrotwardości wykazano, że już niewielki dodatek nanorurek węglowych powoduje zwiększenie twardość nanokompozytu.

6

Influence of the milling time and MWCNT content on the wear properties of the AlMg1SiCu/MWCNT nanocomposites

Dobrzański L. A., Macek M., Tomiczek B., Pakieła W., Kremzer M.

Archives of Materials Science and Engineering

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2015

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Vol. 74, nr 2

77--84

EN

Purpose: In the present article, the wear behaviour of aluminium alloy matrix nanocomposites containing various amounts of carbon nanotubes (0, 2 and 5 vol.%) fabricated using powder metallurgy route has been investigated. Design/methodology/approach: In order to provide the uniform dispersion of the reinforcement particles in the aluminium matrix, in the study, mechanical milling has been used. Through a repeated process of cold welding, fracturing, and re-welding during the mechanical milling, carbon nanotubes are being well embedded between the deformed particles. The tribological test has been performed using a ball-on-plate wear tester. Findings: The microhardness testing has found that addition of carbon nanotubes increases nanocomposite hardness. The results of wear behaviour has showed the influence of the nanocomposite powders preparation conditions on the tribological properties of the final material. Practical implications: Nanocomposites reinforced with carbon nanotubes were prepared using powder metallurgy method what shows the practical implications of the manufacturing of nanocomposites. Originality/value: The results show that because of the simplicity and availability the technology of manufacturing can find the practical application in the production of new light metal matrix nanocomposites. It has been found out that carbon nanotubes, used as reinforcing phase have the influence on the properties of metal matrix composites.

7

EN AW-AlMg1SiCu alloy matrix composite materials reinforced with halloysite particles manufactured by mechanical milling

Dobrzański L. A., Tomiczek B., Pawlyta M., Gołombek K.

Inżynieria Materiałowa

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2014

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Vol. 35, nr 2

102--105

EN

In this work the selected results of microstructure investigations and mechanical properties of the aluminium matrix composite materials reinforced with halloysite particles manufactured by powder metallurgy techniques, including mechanical milling and pressing and hot extrusion following them, are presented. Composite materials were elaborated employing the air atomized powders of aluminium alloy EN AWAlMg1SiCu as a matrix and the halloysite nanotubes as a reinforcement. Composite powders of aluminium alloy matrix reinforced with 5, 10 and 15 wt % of halloysite nanotubes were manufactured by high-energy ball milling using a planetary mill. The obtained composite powders were compacted in the cylindrical matrix of 25 mm in diameter with pressure of 300 MPa and then extruded at 480°C with caning and without degassing. The microstructure of the investigated material was examined by the light microscope and scanning and transmission electron microscope. To determine microhardness suitable tests were performed in the parallel plane related to the extrusion direction with a use of the Vickers hardness tester. The tests were also carry out to determine compressive strength static compression. It has been found that the process of low-energy agitation of the input powders causes relatively uneven distribution of irregular, mostly agglomerated reinforcement particles in the matrix. The composite materials produced in the process of high-energy grinding are characterized by a different structure: the halloysite reinforcement particles are very evenly distributed, rarely forming any agglomerations. The composite materials obtained as a result of mechanical synthesis and hot extrusion are characterized by the structure of evenly distributed, disperse mineral phase particles in fine-grain matrix of EN AW-AlMg1SiCu alloy, thus facilitating the obtainment of higher values of strength properties in comparison to the initial alloy. The nanostructural composite materials reinforced with halloysite particles with 15% mass share are characterized by more than 180% higher plasticity limit and almost twice higher microhardness in comparison to the matrix material.

PL

W pracy przedstawiono wybrane wyniki badań materiałów kompozytowych o osnowie stopu aluminium wzmacnianych cząstkami haloizytowymi wytworzonych z wykorzystaniem metod metalurgii proszków: mechanicznego mielenia oraz kolejno prasowania i wyciskania na gorąco. Badane materiały kompozytowe wytworzono z proszku stopu aluminium EN AW-AlMg1SiCu, stanowiącego materiał osnowy i wzmacnianego nanorurkami haloizytowymi. Do badań przygotowano trzy zestawy próbek zawierających odpowiednio 5, 10 i 15% masowo cząstek wzmacniających, mielonych w wysokoenergetycznym młynie kulowym. Proszki kompozytowe otrzymane w procesie mechanicznego mielenia sprasowano na zimno za pomocą prasy hydraulicznej w formie o średnicy 25 mm pod ciśnieniem 300 MPa, a następnie wyciskano w temperaturze 480°C bez odgazowania, w koszulce osłonowej. Strukturę opracowanych materiałów kompozytowych zbadano za pomocą mikroskopii świetlnej, a także skaningowej i transmisyjnej mikroskopii elektronowej. Sposobem Vickersa zmierzono twardość wyciskanych materiałów kompozytowych na zgładach poprzecznych, a na uniwersalnej maszynie wytrzymałościowej wykonano badania wytrzymałości na ściskanie. W celu oceny wpływu oddziaływania procesu mechanicznego mielenia proszków wyjściowych na własności badanych materiałów kompozytowych w porównaniu z procesem mieszania tych samych proszków zastosowano dwa rodzaje procesu mielenia. Stwierdzono, że proces niskoenergetycznego mieszania proszków wyjściowych powoduje stosunkowo nierównomierne rozłożenie nieregularnych, w większości zaglomerowanych cząstek wzmocnienia w metalowej osnowie. Odmienną strukturą cechują się materiały kompozytowe wytworzone w procesie wysokoenergetycznego mielenia: haloizytowe cząstki wzmacniające są rozłożone bardzo równomiernie, rzadko tworząc skupiska. Otrzymane w procesie mechanicznej syntezy i wyciskania na gorąco materiały kompozytowe charakteryzują się strukturą równomiernie rozłożonych, rozdrobnionych cząstek fazy mineralnej w drobnoziarnistej osnowie stopu EN AW-AlMg1SiCu, sprzyjającą osiąganiu wyższych wartości własności wytrzymałościowych w porównaniu ze stopem wyjściowym. Wytworzone nanostrukturalne materiały kompozytowe wzmacniane cząstkami haloizytowymi o udziale masowym 15% charakteryzują się w porównaniu z materiałem osnowy większą o ponad 180% granicą plastyczności oraz ponad dwukrotnie większą mikrotwardością.

8

High-coercivity Nd-Fe-B Powders Obtained by High-Temperature Milling

Kaszuwara W., Michalski B., Orlowski P.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 1

47--50

EN

The possibility of employing high temperature milling (600°C) for the production of highly coercive Nd-Fe-B powders was examined. The materials were the Nd12Fe82B6, alloy which was subjected to mechanical milling and the powders of the constituent elements of this alloy which were processed by mechanical alloying. The processes were conducted in the two variants: the first variant consisted of mechanical milling performed at a high temperature which was maintained during the entire process, and the other variant included preliminary milling carried out at room temperature and then the milling temperature was increased. All the processes gave nanocrystalline powders with hard magnetic properties. The powders produced by mechanical milling had better properties than those produced by mechanical] alloying as they were more homogeneous and contained smaller amounts of the α-Fe phase.

PL

W pracy badano możliwości zastosowania procesu mielenia w wysokiej temperaturze (600°C) do otrzymywania wyso- kokoercyjnych proszków Nd-Fe-B. Mieleniu poddano stop Nd12Fe82B6,. a także zastosowano metodę mechanicznej syntezy stopów tzn. mielono proszki pierwiastków składników stopu. Procesy prowadzono w dwóch wariantach: cały proces odbywał się w podwyższonej temperaturze lub stosowano wstępne mielenie w temperaturze pokojowej, a następnie mielenie w wysokiej temperaturze. We wszystkich procesach uzyskano nanokrystalicze proszki o właściwościach magnetycznie twardych Proszki uzyskane w procesie mielenia stopu miały właściwości lepsze od proszków otrzymanych w procesie mechanicznej syntezy stopów, ponieważ były bardziej jednorodne i posiadały mniejszy udział fazy α-Fe.

9

Effect of carbon nanotubes content on morphology and properties of AlMg1SiCu matrix composite powders

Dobrzański L., Macek M., Tomiczek B.

Archives of Materials Science and Engineering

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2014

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Vol. 69, nr 1

12--18

EN

Purpose: The main purpose of this work is to determine morphology, as well as technological and mechanical properties of aluminium matrix powder reinforced with multi-walled carbon nanotubes (MWCNTs) using powder metallurgy techniques. Dispersion of the multi-walled carbon nanotubes was achieved by using mechanical milling in a high energy ball mill. The addition of MWCNTs cause significant improvement in mechanical properties of Al/MWCNTs nanocomposites what is confirmed with more than a threefold increase in the hardness of composite powders, as compared to this value before milling. Design/methodology/approach: The main problem of the study is the agglomeration and poor distribution of carbon nanotubes in the matrix material. In order to achieve uniform dispersion of carbon nanotubes in aluminium alloy matrix mechanical milling was used. Additional problem is possible formation of the brittle aluminium carbides in the result of reaction between carbon nanotubes and aluminium particles. Findings: On the basis of micro-hardness testing has found that a small addition of carbon nanotubes in an amount of 0.5% by volume increases composites hardness by 13%, while the addition of carbon nanotubes in an amount of 5% by volume results in an increase of 37%.Practical implications: Composite powders carbon nanotubes were prepared using powder metallurgy method which shows the practical implications in manufacturing of nanocomposites. Originality/value: The investigation results shows that the technology of composite materials manufacturing can find the practical application in the production of new light metal matrix composites. It was found that carbon nanotubes, used as reinforcing phase, have influence on the properties of metal matrix composites.

10

Mechanically milled aluminium matrix composites reinforced with halloysite nanotubes

Dobrzański L.A., Tomiczek B., Adamiak M., Gołombek K.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

654--660

EN

Purpose: The present work describes fabrication of aluminium AlMg1SiCu matrix composite materials reinforced with halloysite nanotubes by powder metallurgy techniques and hot extrusion. Design/methodology/approach: Mechanical milling, compacting and hot extrusion successively are considering as a method for manufacturing metal composite powders with a controlled fine microstructure and enhanced mechanical properties. It is possible by the repeated welding and fracturing of powders particles mixture in a highly energetic ball mill. Findings: The milling process has a huge influence on the properties of powder materials, changing the spherical morphology of as-received powder during milling process to flattened one due to particle deformation followed by welding and fracturing particles of deformed and hardened enough which allows to receive equiaxial particles morphology again. The investigation shows that so called brittle mineral particles yields to plastic deformation as good as ductile aluminium alloy particles. That indicates that the halloysite powder can play a role of the accelerator during mechanical milling. High energy ball milling as a method of mechanical milling improves the distribution of the halloysite reinforcing particles throughout the aluminium matrix, simultaneously reducing the size of particles. The apparent density changes versus milling time can be used to control the composite powders production by mechanical milling and the presence of halloysite reinforcements particles accelerates the mechanical milling process. Research limitations/implications: Contributes to knowledge about technology, structure and properties of aluminium alloy matrix composite material reinforced with mineral nanoparticles. Practical implications: Conducted research shows that applied technology allows obtaining very good microstructural characteristics. Originality/value: It has been confirmed that halloysite nanotubes can be applied as an effective reinforcement in the aluminium matrix composites. Deformation, grain size reduction and dispersion conduce to hardening of the composite powders. Mechanical milling cause a high degree of deformation, decrease the grain size even to nanoscale and create an enormously uniform distribution of reinforcing phases or oxides in the structure of the metal.

11

Mechanical milling of aluminum powder using planetary ball milling process

Ramezan M, Neitzert T

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

790--798

EN

Mechanical alloying has recently attracted considerable attention as researchers strive to enhance nanocomposite properties and extend their utility. The process can be performed at room temperature and homogeneous nanocomposite powders can be produced. In this paper, we investigated the effect of different ball milling parameters and operating conditions (milling time, ball size, processing control agent (PCA) and speed) in mechanical alloying of aluminum powder to achieve particle size reduction with less contamination. Two types of PCA, i.e. stearic acid and methanol have been used and microstructure evolutions at different operating conditions were studied. It was shown that the optimized milling parameters for aluminium composite are 100 stainless steel ball (10 mm), 200 rpm rotation speed with direction reversal and 1 min pause time after every 15 min running time, under argon gas for 30 hr of milling.

12

Manufacturing of EN AW6061 matrix composites reinforced by halloysite nanotubes

Dobrzański L. A., Tomiczek B., Adamiak M.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 1

82--89

EN

Purpose: The core of the work consists in the elaboration of composite materials of aluminium alloy matrix, manufactured with the use of powder metallurgy technologies, including mechanical milling and hot extrusion and in determining the influence of the share of halloysite nanotubes - as the reinforcing phase on the structure and mechanical properties of fabricated composites. Design/methodology/approach: Mechanical milling and hot extrusion are considering as a method for fabricating composite metal powders with a controlled fine microstructure. It is possible by the repeated fracturing and re-welding of powders particles mixture in a highly energetic ball mill. Findings: It has been confirmed that halloysite nanotubes can be applied as a effective reinforcement in the aluminium matrix composites. High energy ball milling as a method of mechanical milling improves the distribution of the halloysite reinforcing particles throughout the aluminium matrix, simultaneously reducing the size of particles. Research limitations/implications: Contributes to research on structure and properties of aluminium alloy matrix composite material reinforced with mineral nanoparticles. Practical implications: The apparent density changes versus milling time can be used to control the composite powders production by mechanical milling and the presence of halloysite reinforcements particles accelerates the mechanical milling process. Conducted research shows that applied technology of composite materials production allows to obtain very good microstructural characteristics. Originality/value: The application of halloysite nanotubes as the reinforcing phase of metal composite materials is a novel assumption of the discussed work and an interesting challenge whereof realization would enable to use this mineral clay in an innovative and cost effective way.

13

The Dehydrogenation Process of Destabilized NaBH4-MgH2 Solid State Hydrie Composites

Czujko T., Varin R. A., Zarański Z., Wroński Z. S.

Archives of Metallurgy and Materials

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2010

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Vol. 55, iss. 2

539-552

EN

The composite behaviour of sodium borohydride – magnesium hydride mixtures was investigated. Mutual influence of both hydrides on their decomposition process was studied. The (NaBH4+MgH2) composite hydride system was synthesized in a wide range of compositions by controlled mechanical (ball) milling in a magneto-mill. In effect, nanocomposites having nanometric grain sizes of the constituent phases residing within micrometric-sized particles were produced. The dehydrogenation process of obtained composites was investigated by Differential Scanning Calorimetry (DSC) method. It is shown that the hydrogen desorption temperature of the composite constituent with the higher desorption temperature in the (NaBH4+MgH2) system substantially decreases linearly with increasing volume fraction of the constituent having lower desorption temperature which is similar behavior to well-known composite Rule-of-Mixtures (ROM) for structural composites. It is also shown that in the (NaBH4+MgH2) composite the constituents such as MgH2 and NaBH4 decompose separately and destabilization of the composite constituent with a higher desorption temperature is unrelated to the formation of MgB2 intermetallic phase. Therefore, the improved dehydrogenation properties for NaBH4 is likely due to the presence of nanostructured metallic Mg which acts as a catalyst. It is also shown that, most likely, the NaBH4 constituent act as a catalyst for the accelerated decomposition of MgH2.

PL

W pracy przedstawiono wyniki badań zachowań kompozytowch mieszaniny borowodorek sodu – wodorek magnezu, gdzie ocenie poddano wzajemne oddziaływanie obu wodorków na ich proces dekompozycji. Układ kompozytów wodorkowych (NaBH4+MgH2) syntetyzowany był w szerokim zakresie składów, poprzez kontrolowane mielenie mechaniczne (kulowe), w młynku magnetycznym. W efekcie powyższego procesu wytworzono nanokompozyty, których składniki fazowe posiadają ziarna o nanometrycznej wielkości, wystepujące w mikrometrycznych cząstkach. Proces odwodorowania uzyskanych kompozytów badano z wykorzystaniem metody kalorymetrycznej DSC (Differential Scanning Calorimetry). Wykazano, że temperatura desorbcji wodoru składnika kompozytu o wyższej temperaturze dekompozycji w układzie (NaBH4+MgH2) istotnie obniża się liniowo wraz ze wzrostem udziału objętościowego składnika o niższej temperaturze dekompozycji, zachowując się w sposób podobny do obowiazującej dla kompozytów strukturalnych reguły mieszanin ROM (Rule-of-Mixtures). Wykazano ponadto, iż w kompozycie (NaBH4+MgH2) jego składniki, MgH2 i NaBH4, dekomponuja oddzielnie i destabilizacja składnika o wyższej temperaturze desorbcji nie jest związana z powstawaniem fazy międzymetalicznej MgB2. Stąd też poprawa właściwości do odwodorowania NaBH4 jest prawdopodobnie spowodowana obecnoącią nanostrukturalnego, metalicznego Mg, który działa katalitycznie. Dodatkowo wykazano, że NaBH4 najprawdopodobniej działa katalitycznie na przyspieszenie dekompozycji MgH2.

14

The effects of microstructural modification by mechanical milling on hydrogen desorption from magnesium hydride

Varin R. A., Czujko T., Wronski Z. S., Calka A.

Journal of KONES

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2007

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Vol. 14, No. 2

529-536

EN

Nanostructured hydrides fabricated by mechanical (ball) milling offer a promising alternative to hydrogen storage in compressed or liquid form. However, ball milling brings about both beneficial and detrimental effects to their hydrogen desorption characteristics. These effects have been studied in the ball milled magnesium hydride, MgH2. A beneficial effect is that the refinement of the hydride powder particle size and the gamma-MgH2 phase residing within the powder particles, acting additively, are responsible for a substantial reduction of hydrogen desorption temperature of MgH2 hydride. A detrimental effect is a reduction of the hydrogen storage capacity after nanostructuring of MgH2 by ball milling. Both effects are presented and discussed. In particular DSC hydrogen desorption curves at the heating rate of 4°C/min of the ABCR powder as received, milled in hydrogen for (a) 0.25 to 5h and (b) 10 and 20h and finally cycled, XRD patterns of MgH2 (Tego Magnan registered trademark) powders milled continuously for 100h, desorption curves under 0.1 MPa H2 at various temperatures of commercial MgH2 powder Tego Magnan registered trademark milled continuously for 20h are presented in the paper.

15

Nanocrystalline magnesium and its properties of hydrogen sorption

David E.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

87-90

EN

Purpose: The goal of this paper is to study the possibility of obtaining of magnesium and magnesium hydride in nanocrystalline form and then to activate these materials for to be used in efficient systems of hydrogen storage. Design/methodology/approach: The magnesium hydride (MgH2) was directly synthesized from mechanically grinded magnesium powder obtained through ball milling of Mg(BM), and hydrogen of high purity. The MgH2 was then chemical activation by surface modification of nanocrystalline Mg with nickel ultrafine particles addition. The hydrogen sorption properties of the nanocrystalline Mg were investigated by a conventional pressure-volume-temperature technique, X-ray diffraction, and scanning electron microscopy (SEM). Findings: We found that the mechanical activation improved significantly the kinetics of hydrogen absorption in nanocrystalline magnesium, increasing sorption rates by up to 2 orders of magnitude. A profound effect of the powder particle size on the hydrogen desorption characteristics has been also observed. It was also determined that the Mg2Ni compound absorbed hydrogen quickly and showed excellent hydrogen sorption properties at 300 degrees centigrade. Research limitations/implications: The reduction of the particle size of magnesium and the creation of fresh surfaces by mechanical ball milling help the kinetics but does not affect the thermodynamics. Practical implications: Further examination to obtain improved properties of hydrogen sorption process of magnesium based materials and investigations of achievement of new systems for hydrogen solid storage. Originality/value: This work contains new aspects, which show the conditions of obtaining of nanocrystalline metal clusters with size under 30nm and represents new approach of improvement of hydrogen sorption process in light metals, such as magnesium, that can provide promising results for hydrogen storage applications.

16

Struktura i wybrane własności materiałów kompozytowych o osnowie stopu EN AW6061 wzmacnianych cząstkami faz międzymetalicznych Ti3Al

Adamiak M.

Kompozyty

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2006

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R. 6, nr 2

70-75

PL

Przedstawiono wyniki badań nad możliwością wytwarzania materiałów kompozytowych o osnowie stopu aluminium EN AW6061 wzmacnianych cząstkami fazy międzymetalicznej Ti3Al w procesach metalurgii proszków i wyciskania na gorąco. Stwierdzono, że proces mechanicznego mielenia w zasadniczy sposób oddziałuje na własności materiałów proszkowych poprzez zmianę ich morfologii ze sferycznej, charakterystycznej dla stanu wyjściowego, w odkształconą plastycznie - płatkową, która następnie w powtarzających się procesach zgrzewania i pękania materiału umocnionego ponownie przyjmuje postać cząstek równoosiowych. Wykonane badania pozwoliły stwierdzić ponadto, że cząstki fazy międzymetalicznej odkształcają się plastycznie podobnie jak cząstki materiału osnowy, a zatem cząstki fazy międzymetalicznej Ti3Al w przeciwieństwie do cząstek ceramicznych nie wpływają na przyspieszenie procesu mechanicznego mielenia. Wytworzone materiały kompozytowe charakteryzują się równomiernym rozłożeniem rozdrobnionych cząstek wzmacniających, wpływającym na podwyższenie własności mechanicznych. W porównaniu do materiałów kompozytowych wytworzonych przez wyciskanie zmieszanych proszków materiałów wyjściowych, dla których dodatek cząstek wzmacniających powoduje wzrost twardości o 20-25 HV1, mechaniczne mielenie tych samych proszków z utworzeniem proszków kompozytowych powoduje dwukrotny wzrost twardości w odniesieniu do materiału osnowy. Rozdrobnienie mikrostruktury w połączeniu z dyspersyjnym umocnieniem materiału od cząstek wzmacniających prowadzi do znaczącej poprawy własności mechanicznych. Materiały kompozytowe z 15% wagowym udziałem cząstek Ti3Al osiągają wytrzymałość na rozciąganie Rm ok. 400 MPa.

EN

The present work investigates the production of aluminium EN AW6061 matrix composite materials reinforced with Ti3Al particles by powder metallurgy techniques and hot extrusion. The introduction of new reinforcements such as inter-metallics to aluminium alloys continues to be investigated in order to improve final behaviour of AMCs as well as to avoid some drawbacks of using ceramics as aluminium alloys reinforcements. The milling process has a big influence on the characteristics of powder materials, changing the spherical morphology of as-received powder (Fig. 1), during milling process to flattened one due to particle deformation (Fig. 2), followed by welding and fracturing particles of deformed and hardened enough which allows to receive equiaxial particles morphology again (Fig. 3). The investigation shows that so called brittle intermetallic particles yields to plastic deformation as good as ductile aluminium alloy particles. That indicates that in contrary to ceramics particle, the Ti3Al intermetallic powder can not play a role of the accelerator during mechanical milling. The mechanically milled and extruded composites show finer and better distribution of reinforcement particles what leads to better mechanical properties of obtained products (Fig. 5). The hardness increases twice in case of mechanically milled and only 20-25 HV1 for low energy mixed and hot extruded composites (Fig 6.) The finer microstructure increase mechanical properties of composites materials. The higher reinforcement content results in higher particles dispersion hardening (Fig 7). Composites reinforced with 15% of Ti3Al reach about 400 MPa UTS.

17

Influence of the chemical composition and particle size of the metal matrix, on TiCN-reinforced Fe-based composites

Gómez B., Gordo E., Ruiz-Navas E. M., Torralba J. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

57-60

EN

Purpose: The objective of this work is to study the influence of different parameters as the chemical composition and particle size of the metal matrix, on TiCN-reinforced Fe-based composites. Design/methodology/approach: In order to obtain the composite powder two different types of blending were used, conventional blending and high energy milling (HEM). The HEM was carried out in a planetary ball mill during 12 hours, with a rotating speed of 400 rpm, and a ratio ball:powder of 10:1 (in mass). The atmosphere was Argon to prevent the oxidation. After the preparation of powders, compacts were produced by uniaxial pressing at 700 MPa and sintering under vacuum. The sintering temperatures varied between 1350oC and 1450oC, for 60 min. Sintered samples were characterised by determination of density, dimensional change, Vickers hardness (HV30), bending strength, and C, N contents (by LECO). The microstructural study was carried out by scanning electron microscopy (SEM). Findings: As a result of the study it is clear that the presence of carbides in the metal matrix allows the increasing of mechanical properties of sintered composites, and these properties are related with the microstructure and C/N ratio. Practical implications: In this research 50 % vol of hard phase is introduced, following a simpler and lowercost route, as pressing and sintering. It is true that high-energy milling raises the cost of the processing. This is why conventional blending of small size powder particle has also been done in this work. The latter route has shown to give quite promising results, reaching hardness values about 2000 HV30. Originality/value: In this work, composite materials with high hardness have been obtained following a simple and low-cost route.

18

Zastosowanie mechanicznego mielenia do wytwarzania materiałów kompozytowych

Adamiak M.

Archiwum Odlewnictwa

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2006

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R. 6, nr 21/2

361--368

PL

W ramach pracy wykonano badania nad możliwością wytwarzania materiałów kompozytowych o osnowie stopu aluminium EN AW6061 wzmacnianych cząstkami fazy międzymetalicznej Ti3Al w procesie mechanicznego mielenia, a następnie prasowania proszków i wyciskania na gorąco. Stwierdzono, że zmieniając czas trwania procesu mechanicznego mielenia w zasadniczy sposób oddziałuje się na morfologię materiałów proszkowych, uzyskując zmianę ich morfologii ze sferycznej charakterystycznej dla stanu wyjściowego w odkształconą plastycznie - płatkową, która następnie w powtarzających się procesach zgrzewania i pękania materiału umocnionego ponownie przyjmuje postać cząstek równoosiowych. Wytworzone materiały kompozytowe charakteryzują się równomiernym rozłożeniem rozdrobnionych cząstek wzmacniających wpływającym na podwyższenie własności mechanicznych. Mechaniczne mielenie proszków wyjściowych z utworzeniem proszków kompozytowych poprzez rozdrobnienie mikrostruktury w połączeniu z dyspersyjnym umocnieniem materiału od cząstek wzmacniających powoduje dwukrotny wzrost twardości w odniesieniu do materiału osnowy, także prowadzi do znaczącej poprawy własności mechanicznych. Materiały kompozytowe z 15% wagowym udziałem cząstek Ti3Al osiągają wytrzymałość na rozciąganie Rm ok. 400 MPa.

EN

The present work investigates the production of aluminium EN AW6061 matrix composite materials reinforced with Ti3Al particles by mechanical milling followed by powder metallurgy techniques and hot extrusion. It was find out that mechanical milling process has a big influence on the characteristics of powder materials, changing the spherical morphology of as-received powder, during milling process to flattened one due to particle deformation, followed by welding and fracturing particles of deformed and hardened enough which allows to receive equiaxial particles morphology again. The mechanically milled and extruded composites show finer and better distribution of reinforcement particles what leads to better mechanical properties of obtained products. The hardness increases twice in case of mechanically milled and hot extruded composites. The finer microstructure increase mechanical properties of composites materials. The higher reinforcement content results in higher particles dispersion hardening. Composites reinforced with 15% of Ti3Al reach about 400 MPa UTS.

19

Particle fracture and phase transformations induced by electrical discharge assisted mechanical milling

Calka A., Wexler D.

Inżynieria Materiałowa

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2004

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R. XXV, nr 3

465-468

EN

A novel device for milling, incorporating high voltage, low current electrical discharges was constructed and its application for materials processing investigated [1, 2]. This type of milling has been found to result in rapid fracture rates, enhanced mechano-chemical reactions and novel reaction paths. We present recent studies of fracturing, agglomeration and phase formation using this method applied to a vibrational rod mill. The effect of spark discharge milling condition on particle size and surface morphology was investigated for a number of different materials including; alumina, NiZr, Ni plus Si, Mg-Zn alloy of eutectic composition. In these experiments, variations in milling vibrational amplitude resulted in variations in nominal average spark length for samples discharged milled under repeated impact. It was confirmed that during discharge milling, rapid fracturing occurs wervery short milling times and is accompanied by the formation of both fine particles and agglomerates. Large vibrational amplitudes tended to promote increased particle agglomeration in both ceramics and metals, while discharge milling with lower vibrational amplitudes promoted the formation of finer particles and smaller agglomerates. In the case of alumina, particle coarsening and spheroidisation was believed to result from repeated sintering of individual particles. For metals, alloys and metallic glasses, the tendency for coarsening and formation of spherical particles resulted from some combination of partial melting and deformation. Spark milling of Mg-Zn eutectic decomposition product was found to result in formation of the metastable eutectic phase, Mg7Zn3.

20

Wpływ metod wytwarzania na właściwości nanokrystalicznych magnesów Sm-Fe-N.

Kaszuwara W., Leonowicz M., Wysłocki J. J., Wysłocki B.

Archiwum Nauki o Materiałach

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2003

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T. 24, nr 4

327-342

PL

Badania przeprowadzono na nanokrystalicznych magnesach Sm-Fe-N wytwarzanych różnymi metodami: mechanicznej syntezy (MA), długotrwałego mielenia (MM), szybkiego chłodzenia ze stanu ciekłego (RS) i wykorzystując rozkład i rekombinację fazy magnetycznie twardej w procesie nasycania wodorem (HDDR). Rodzaj zastosowanej metody wytwarzania magnesów Sm-Fe-N wpływa istotnie na uzyskiwaną mikrostrukturę (wielkość ziarna oraz skład fazowy) i właściwości magnetyczne materiału. Ponadto wyznaczono podstawowe mikromagnetyczne parametry nanokrystalicznych magnesów Sm-Fe-N oraz ich faz składowych.

EN

Investigations were carried out on nanocrystalline Sm-Fe-N magnets produced by different methods: mechanical alloying (MA), mechanical milling (MM), rapid solidification from liquid state (RS) and using disproportionation and recombination of hard magnetic phase during hydrogenation process (HDDR). The different type of applied production method of the Sm-Fe-N magnets influences essentially the microstructure (grain size and phase composition) and magnetic properties of the material. Moreover, basic intrinsic magnetic parameters of nancrystalline Sm-Fe-N magnet and its constituent phases were determined.