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EN
In the paper, hydrogenation and corrosion properties of three kinds of nanocrystalline La1.5Mg0.5Ni7 type alloys obtained by mechanical alloying (MA) method are discussed in view of their application as anodic materials for Ni/MH batteries. Partial substitutions of cobalt for nickel and gadolinium for lanthanum and then magnetron sputtering of the intermetallic powders with amorphous nickel distinctly change functional parameters of the hydrogen storage material. It is shown that 5.5 at.% cobalt addition markedly improves the alloy activation but worsens its corrosion resistance in concentrated KOH solution. On the other hand, partial substitution of lanthanum by Gd (2.2 at.%) ensures large exchange currents for H2O/H2 system. Presence of Ni coatings on alloy particles is generally advantageous from the material H-storage properties, although they slow down a little hydrogen transport during electrode discharge.
PL
W artykule przedyskutowano właściwości wodorochłonne i korozyjne trzech rodzajów nanokrystalicznych stopów typu La1.5Mg0.5Ni7 – pod kątem ich aplikacji jako materiałów anodowych dla ogniw typu Ni/MH. Materiały wytwarzano metodą mechanicznej syntezy (metoda MA) i modyfikowano poprzez częściowe podstawianie niklu kobaltem bądź lantanu gadolinem a następnie poprzez magnetronowe napylanie uzyskanych proszków amorficznym niklem. Modyfikacje te wyraźnie zmieniają właściwości funkcjonalne badanych stopów wodorochłonnych. Pokazano, że dodatek 5,5 % at. kobaltu wyraźnie skraca aktywację stopu ale pogarsza jego odporność korozyjną w stężonym roztworze KOH. Z kolei częściowe podstawienie lantanu gadolinem (2,2 % at.) zapewnia materiałowi wysokie gęstości prądu wymiany układu H2O/H2. Obecność powłok Ni na cząstkach proszku jest generalnie korzystna z punktu widzenia właściwości sorpcyjnych materiałów, jednakże powłoki te nieco hamują transport wodoru podczas rozładowywania elektrod.
EN
Purpose: This paper explains mechanical synthesis which uses powders or material chunks in order to obtain phases and alloys. It is based on an example of magnesium powders with various additives, such as zinc, calcium and yttrium. Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD) method, scanning electron microscopy (SEM), determining particle size distributions with laser measuring, Vickers microhardness. Findings: The particle-size of a powder and microhardness value depend on the milling time. Research limitations/implications: Magnesium gained its largest application area by creating alloys in combination with other elements. Magnesium alloys used in various industry contain various elements e.g. rare-earth elements (REE). Magnesium alloys are generally made by casting processes. Consequently, the search for new methods of obtaining materials such as mechanical alloying (MA) offers new opportunities. The MA allows for the production of materials with completely new physico-chemical properties. Originality/value: Thanks to powder engineering it is possible to manufacture materials with specific chemical composition. These materials are characterized by very high purity, specified porosity, fine-grain structure, complicated designs. These are impossible to obtain with traditional methods. Moreover it is possible to refine the process even further minimalizing the need for finishing or machining, making the material losses very small or negligible. Furthermore material manufactured in such a way can be thermally or chemically processed without any problems.
EN
The effect of replacing iron with transition metals (M = Mn, Cr, Co) on the microstructure of mechanically alloyed Al65 Cu20 Fe15 quasicrystalline powder was examined by X-ray diffraction and transmission electron microscopy methods. Powders of various compositions were milled in a high-energy planetary ball mill up to 30 hours at a rotation speed 350 rpm using WC milling media. The amount of the fourth additions was constant in all powders and Fe atoms were replaced with Mn, Cr or Co in a 1:1 ratio, while the content of the Al and Cu was selected in two ways: they remained the same as in the initial ternary Al65 Cu20 Fe15 alloy or changed to obtain e/a ratio = 1.75 (optimal for icosahedral quasicrystalline phase). Quasicrystalline phase formed in the quaternary Al65 Cu20 Fe7.5 M7.5 powders, whereas in the second group of compositions only crystalline phases were identified.
EN
The paper presents the results of research on the Al-V2O5 composite manufactured by means of the mechanical alloying and powder metallurgy method. Observation of the microstructure and X-ray chemical composition (XRD) analysis of the composite after extrusion were carried out. One of the most desirable features of metallic composites – apart from mechanical properties – is their resistance to increased impact temperature. It was observed that the formation of intermetallic phases due to the chemical reaction between strengthening particles and the composite matrix depends primarily on the annealing conditions of the material. The hardness of the annealed samples, depending on the annealing temperature, were discussed with respect to the material microstructure transformation. Despite the high-temperature, annealing at 473–773K, the material hardness did not change significantly, and remained approx.125 HV. However, at higher annealing temperatures, i.e. 823K, the chemical reaction between the components leads to the formation of the Al10V particles and increases hardness.
PL
W pracy przedstawiono wyniki badań kompozytu Al-V2O5, który wytworzono metodą mechanicznej syntezy. Przeprowadzono obserwację mikrostruktury oraz rentgenowską analizę składu chemicznego (XRD) kompozytu po procesie wyciskania. Jedną z najbardziej pożądanych cech kompozytów metalicznych – oprócz własności mechanicznych – jest ich odporność na oddziaływanie podwyższonej temperatury. Powstawanie faz międzymetalicznych na skutek reakcji chemicznej pomiędzy cząstkami umacniającymi a osnową kompozytu zależy przede wszystkim od warunków wyżarzania materiału kompozytowego. W pracy przedstawiono zależność twardości od temperatury wyżarzania (473–823 K). Twardość materiału nie zmienia się znacząco w dość wysokiej temperaturze wyżarzania jak w przypadku aluminium (473–773 K), a jej wartość osiąga średni poziom 125HV2. Stwierdzono, że reakcja chemiczna między składnikami podczas wyżarzania w temperaturze 823 K prowadzi do powstania fazy międzymetalicznej Al10V, co powoduje wzrost twardości kompozytu.
EN
The effects of different types of process control agents (PCA) on the microstructure evolution of Ni-based oxide dispersion-strengthened superalloy have been investigated. Alloy synthesis was performed on elemental powders having a nominal composition of Ni-15Cr-4.5Al-4W-2.5Ti-2Mo-2Ta-0.15Zr-1.1Y2O3 in wt % using high energy ball milling for 5 h. The prepared powders are consolidated by spark plasma sintering at 1000°C. Results indicated that the powder ball-milled with ethanol as PCA showed large particle size, low carbon content and homogeneous distribution of elemental powders compared with the powder by stearic acid. The sintered alloy prepared by ethanol as PCA exhibited a homogeneous microstructure with fine precipitates at the grain boundaries. The microstructural characteristics have been discussed on the basis of function of the PCA.
EN
Ag and Cu powders were mechanically alloyed using high-energy planetary milling to evaluate the sinter-bonding characteristics of a die-attach paste containing particles of these two representative conductive metals mixed at atomic scale. This resulted in the formation of completely alloyed Ag-40Cu particles of 9.5 μm average size after 3 h. The alloyed particles exhibited antioxidation properties during heating to 225°C in air; the combination of high pressure and long bonding time at 225°C enhanced the shear strength of the chip bonded using the particles. Consequently, the chips sinter-bonded at 225°C and 10 MPa for 10 min exhibited a sufficient strength of 15.3 MPa. However, an increase in bonding temperature to 250°C was detrimental to the strength, due to excessive oxidation of the alloyed particles. The mechanically alloyed phase in the particle began to decompose into nanoscale Ag and Cu phases above a bonding temperature of 225°C during heating.
PL
W artykule przedstawione zostały własności technologiczne proszków kompozytowych Cu/TiN, które mają istotny wpływ na zdolność proszku do zagęszczenia, a w konsekwencji na dalsze procesy prasowania i spiekania. Gęstość nasypowa, gęstość nasypowa z usadem, jak i sypkość proszku, zależy przede wszystkim od kształtu cząstek, ich rozmiaru, jak również chropowatości powierzchni. Badaniom własności technologicznych poddane zostały mieszanki proszków kompozytowych na osnowie miedzi z 5, 10 i 15% wag. dodatkiem azotku tytanu. Proszki kompozytowe Cu/TiN wytworzone zostały na drodze mechanicznej syntezy, gdzie czas mielenia wyniósł 10 h.
EN
This article presents the technological proporties of Cu/TiN composite powders which have significant impact on the powder’s ability to compaction and consequently on further pressing and sintering process. Bulk density, tap density and powders flowability depends primarily on the shape of the particles, their size and surface roughness. In the article, the investigations of technological proporties were subjected to mixtures of composite powders on a copper reinforced with 5, 10, 15% wt. TiN. Addition of titanium nitride. Cu/TiN composite powders were produced by mechanical alloying, where the milling time was 10 hours.
EN
The development of a new deposition method allowing to obtain thick composite coatings is of both scientifically and practical importance. The one presented in this paper is based on a negative side effect taking place during the mechanical synthesis of alloys, i.e. sticking of milled material to the surfaces of both the vial and balls. The experiment covered the comilling of NiAl (~45 µm) with 15 wt.% CrB2 (~40 µm) powders together with nickel platelets used as the substrates and steel balls. The above processing performed at 200 rpm resulted in a steady increase in the thickness of the rubbed-in buildup on the platelet surfaces allowing coatings of 4, 11, 22 and 33 µm to be produced after 4, 8, 16 and 32 hours. The OM, XRD and TEM investigations showed that such coatings are characterized by a gradient microstructure with heavily dislocated but coarser grains near the substrate and a more porous inner part formed with rounded well fused agglomerates of greatly refined crystallites. The CrB2 were only slightly larger than the NiAl ones and were distributed quite uniformly. Most of the coating was found well fused with the substrate, but occasional voids and porosity at the substrate/coating interface were also noted. It is worth noting that applying the proposed method allowed the authors to produce a thick, gradient and mostly nano-crystalline NiAl and CrB2 composite coating.
PL
Rozwój nowych metod osadzania powłok kompozytowych jest istotny z naukowego i praktycznego punktu widzenia. Metoda proponowana obecnie bazuje na negatywnym zjawisku zachodzącym w czasie mechanicznej syntezy stopów, tj. oklejaniem mielonym materiałem kul i naczynia w którym prowadzony jest proces. Obecny eksperyment obejmował współmielenie stalowymi kulami proszków NiAl (~45 μm) z 15 wt.% CrB2 (~40 μm) z płytkami Ni zastosowanymi jako podłoża. Proces ten, prowadzony przy 200 obr./min, skutkował ciągłym powiększaniem grubości powłok do 4, 11, 22 i 33 μm odpowiednio po 4, 8, 16 i 32 godz. Badania z wykorzystaniem mikroskopii optycznej, transmisyjnej oraz dyfraktometrii rentgenowskiej wykazały, że powłoki te charakteryzuje budowa gradientowa z warstwą silnie zdefektowanych, ale stosunkowo dużych krystalitów przy podłożu stopniowo zastępowanych nanokrystalicznym porowatym materiałem w formie silnie spojonych aglomeratów. Krystality CrB2 wykazywały niewiele mniejsze rozdrobnienie od NiAl oraz w przybliżeniu równomierny rozkład w intermetalicznej osnowie. Powłoki w większej części wykazywały dobre spojenie z podłożem, ale obecność pustek oraz porowatości penetrującej od granic z podłożem była dokumentowana. Należy podkreślić, że zastosowanie proponowanej metody umożliwia wytworzenie grubych, gradientowych i w przeważającej części nanokrystalicznych kompozytowych powłok.
EN
Mg60 Zn35 Ca5 amorphous powder alloys were synthesized by mechanical alloying (MA) technique. The results of the influence of high-energy ball-milling time on amorphization of the Mg60 Zn35 Ca5 elemental blend (intended for biomedical application) were presented in the study. The amorphization process was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). Initial elemental powders were mechanically alloyed in a Spex 8000 high-energy ball mill at different milling times (from 3 to 24 h). Observation of the powder morphology after various stages of milling leads to the conclusion that with the increase of the milling time the size of the powder particles as well as the degree of aggregation change. The partially amorphous powders were obtained in the Mg60 Zn35 Ca5 alloy after milling for 13-18h. The results indicate that this technique is a powerful process for preparing Mg60 Zn35 Ca5 alloys with amorphous and nanocrystalline structure.
EN
Discovery of superconductivity of MgB2 with a critical temperature of -234 °C has offered the promise of important large-scale applications. Except for the other featured synthesis methods, mechanical activation, performed by high-energy ball mills to synthesis of bulk form of MgB2 or as a first step of wire and thin film production has considered as an effective alternative production route in recent years. The aim of the present study was to determine the effect of process variables such as the ball-to-powder weight ratio (BPR), size of ball, milling time, annealing temperature and contribution of process control agent (toluene) on the product size, morphology and conversion level of precursor powders to MgB2 after subsequent heat treatment. Although, the test results revealed relatively lower weight percent of MgB2 phase formation compared with the literature, the reduced milling time, BPR and sinterability of pre-alloyed powder to MgB2 at lowered temperature (630 °C) enhanced the applicability of mechanical alloying with SPEX mill.
EN
Copper matrix composites containing ceramic particles such as carbides, borides, or nitrides have attracted much attention over the last few years. The increased interest in such materials has mainly been created by their high electrical and thermal conductivity, good mechanical and tribological properties, and microstructural stability. Among other nitrides, the titanium nitride seems to be considered as an attractive reinforcement due to its high hardness, excellent electrical conductivity, and stability at high temperatures. Moreover, its good corrosion resistance proves the uniqueness of the TiN particles above any other nitrides. In this work, Cu-10 wt.% TiN composite powders were produced by mechanical alloying and sintered by the spark plasma sintering (SPS) technique under different temperatures. The morphology and powder particle size after mechanical synthesis were inspected by a scanning electron microscopy (SEM) for all of the powder samples; chemical composition analyses (EDS) were also performed. The hydrostatic method was used to measure the density of the composite samples to analyze the influence of milling time on the process of consolidation in the composite powders.
PL
Kompozyty na osnowie miedzi zbrojone cząstkami ceramicznymi, m.in. węglikami, borkami i azotkami, w ostatnich latach wzbudziły spore zainteresowanie z uwagi na wysoką przewodność cieplną i elektryczną oraz dobre właściwości mechaniczne i tribologiczne przy równoczesnym zachowaniu stabilnej mikrostruktury. Zastosowanie azotku tytanu jako zbrojenia kompozytu jest korzystne ze względu na: wysoką twardość, doskonałą przewodność elektryczną, odporność na korozję oraz stabilność w wysokich temperaturach. W pracy przedstawiono mieszankę kompozytową Cu-10% wag. TiN, wytworzoną w procesie mechanicznej syntezy, którą następnie poddano spiekaniu za pomocą iskrowego spiekania plazmowego (SPS). Zbadano mikrostrukturę, wielkość cząstek, a także przeprowadzono analizę składu chemicznego (EDS, Energy Dispersive Spectroscopy) za pomocą skaningowego mikroskopu elektronowego (SEM). Metodą hydrostatyczną wykonano pomiar gęstości wytworzonych spieków w celu analizy wpływu czasu mielenia na proces konsolidacji proszku kompozytowego.
EN
MA956 (Fe-Cr-Al) alloy powder was high-energy ball milled with various amount of yttria contents (1,2,3, and 4 wt.%) to fabricate an oxide dispersion strengthened alloy. The milled powders were then consolidated using hot press sintering at 1150°C. The surface morphology and crystal structure of MA956 powder during the high-energy milling depending on the yttria contents was investigated using particle size analysis, X-ray diffraction, and scanning electron microscopy. The microstructural analysis of sintered alloy was performed using transmission electron microscopy and energy dispersive spectroscopy to evaluate the dispersion behavior of yttrium oxide. The results showed that, as yttria contents increased, the oxide particles became finer and are uniformly distributed during the high-energy milling. However, after the sintering, the oxide particles were coarsened with more than 3 wt.% of yttria addition.
EN
Titanium β-type alloys are a class of interesting biomaterials that can exhibit a unique combination of mechanical as well as physicochemical and biological properties. The aim of this study is to develop a titanium-molybdenum alloys (Ti-x at % Mo, x = 15 and 23). These materials were prepared by the combination of mechanical alloying and powder metallurgical process. The details of the processing method were presented. The samples were characterized by X-ray diffraction, scanning electron micros-copy, chemical composition determination as well as density and Vickers microhardness measurements. The corrosion behaviour in Ringer solution was investigated, too. The crystallization of the obtained material upon annealing led to the formation of a near single β type alloys. The molybdenum content in titanium and heat treatment parameters of a nearly amorphous phase allow to synthesize Ti(β)-type alloys. The present study has demonstrated that Ti23Mo alloy can be the next generation of biomaterial for bone tissue engineering.
EN
In the present work, we have examined the effect of Ti on the properties of Fe-Y2O3 alloys. The result showed that the addition of Ti was effective for improving mechanical properties. This is due to the reduction of oxides by Ti during mechanical alloying and hot-consolidation. In particular, iron oxides are effectively reduced by the addition of Ti. Compared to the pristine Fe-Y2O3 alloys, titanium-added alloys exhibited fine and uniform microstructures, resulting in at least 60% higher tensile strength.
EN
Characteristics of electro-discharge-sintering of the Ti-37.5at.% Si powder mixture was investigated as a function of the input energy, capacitance, and discharge time without applying any external pressure. A solid bulk of Ti5Si3 was obtained only after in less than 129 μsec by the EDS process. During a discharge, the heat is generated to liquefy and alloy the particles, and which enhances the pinch pressure can condensate them without allowing a formation of pores. Three step processes for the self-consolidation mechanism during EDS are proposed; (a) a physical breakdown of oxide film on elemental as-received powder particles, (b) alloying and densifying the consolidation of powder particles by the pinch pressure, and (c) diffusion of impurities into the consolidated surface.
EN
Electrical discharges using a capacitance of 450 μF at 0.5, 1.0, and 1.5 kJ input energies were applied in a N2 atmosphere to obtain the mechanical alloyed Ti3Al powder without applying any external pressure. A solid bulk of nanostructured Ti3Al was obtained as short as 160 μsec by the Electrical discharge. At the same time, the surface has been modified into the form of Ti and Al nitrides due to the diffusion process of nitrogen to the surface. The input energy was found to be the most important parameter to affect the formation of a solid core and surface chemistry of the compact.
EN
The paper presents the preparation of Ti-(1-30wt.%)Y2O3 composites using the mechanical alloying process. Ti based materials are the best metallic biomaterials because of their excellent properties: biocompatibility, low Young moduli and high corrosion resistance. Pure Ti and Y2O3 powders were alloyed under argon atmosphere in shaker type mill (Spex 8000) followed by pressing and sintering. The ultra-low grain size structure improves the mechanical properties and hardness of the new materials in comparison to microcrystalline Ti-based sinters. However, because of the porosity of approx. 20-30%, a decrease in the Young modulus is observed. Moreover, the new composites show good tendency towards covering by Ca-P compounds during soaking in SBF.
EN
In this work, p-type Bi0.5Sb1.5Te3 alloys were fabricated by high-energy ball milling (MA) and spark plasma sintering. Different revolutions per minute (RPM)s were used in the MA process, and their effect on microstructure, and thermoelectric properties of p-type Bi0.5Sb1.5Te3 were systematically investigated. The crystal structure of milled powders and sintered samples were characterized using X-ray diffraction. All the powders exhibited the same morphology albeit with slight differences find at 1100 RPM conditions. A slight grain size refinement was observed on the fracture surfaces from 500 to 1100 RPM specimens. The temperature dependence of Seebeck coefficient, electrical conductivity, and power factors were measured as a function of temperature with different RPM conditions. The power factor shows almost same (~3.5 W/mK2 at RT) for all samples due to unchanged Seebeck and electrical conductivity values. The peak ZT of 1.07 at 375K is obtained for 1100 RPM specimen due to low thermal conductivity.
EN
In this study, p-type Bi0.5Sb1.5Te3 based nanocomposites with addition of different weight percentages of Ga2O3 nanoparticles are fabricated by mechanical milling and spark plasma sintering. The fracture surfaces of all Bi0.5Sb1.5Te3 nanocomposites exhibited similar grain distribution on the entire fracture surface. The Vickers hardness is improved for the Bi0.5Sb1.5Te3 nanocomposites with 6 wt% added Ga2O3 due to exhibiting fine microstructure, and dispersion strengthening mechanism. The Seebeck coefficient of Bi0.5Sb1.5Te3 nanocomposites are significantly improved owing to the decrease in carrier concentration. The electrical conductivity is decreased rapidly upon the addition of Ga2O3 nanoparticle due to increasing carrier scattering at newly formed interfaces. The peak power factor of 3.24 W/mK2 is achieved for the base Bi0.5Sb1.5Te3 sintered bulk. TheBi0.5Sb1.5Te3 nanocomposites show low power factor than base sample due to low electrical conductivity.
EN
Due to its interesting properties and wide applications in different industries, fabrication of monolithic NiTi with cost-effective methods is an important and attractive issue. One of the economic ways to fabricate NiTi is employing elemental nickel and titanium powders. In this study, effects of using elemental powders as a precursor on the microstructure and mechanical properties of HIP-consolidated NiTi samples will be explored. The result of XRD analysis showed that after HIP process an interwoven structure which consists of NiTi2, Ni3Ti and B2-B19′ NiTi evolves. The formation of NiTi2/Ni3Ti intermetallics is thermodynamically favored which affects different aspects of this alloy: (i) it alters martensitic transformation temperatures; (ii) restricts essential properties of this alloy such as PE and SME, (iii) increases hardness, and (iv) yields to premature fracture at small strains during tensile tests.
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