Wyniki 11-16 spośród 16 dla zapytania: authorDesc:"JAN DUTKIEWICZ"

Ball milling amorphization and consolidation of NiTiZrNb and NiNbTiZrCoCu alloys

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Amorphous nickel rich alloys have been obtained in recent years by rapid quenching from the liquid state or by mechanical alloying in a planetary mill [1÷9]. One advantage of the latter method is that it makes it possible to obtain new materials from powders of different elements, which are immiscible in the liquid state. Binary NiTi alloys subjected to ball milling or severe plastic deformation can be obtained amorphous [1÷3]. The tendency to form an amorphous structure depends on the relative values of the deformation temperature and martensite start (Ms) temperature. Lowering of the deformation temperature in the range below the martensite finish temperature facilitates amorphization [3]. Mechanical alloying of Ni60Nb20Zr20 alloy [4] involves two consecutive amorphization reactions, leading first to the amorphization reaction between Ni and Zr layers and on further milling consequently a Ni-Nb amorphous phase forms. The resulting two amorphous phases homogenize at longer milling times. Multicomponent nickel base alloys can be obtained as bulk glass at composition of Ni50Co10Nb20Ti10Zr10 (at. %) alloys with reported large supercooled liquid region of more than 40 K formed by copper-mold casting. The alloys with 5 and 10 at. % cobalt possess the highest glass-forming ability [5]. Mechanically alloyed Ni57Zr20Ti18Al5 alloy powders synthesized by high-energy ball milling have shown a complete amorphization after 5 h of milling, even broader supercooled region of 56°C and crystallization temperature above 500°C [6]. Substitution of aluminum by silicon [7] also allowed to obtain amorphous Ni57Zr20Ti20Si3 powders by mechanical alloying of pure Ni, Zr, Ti, Si, and ceramic powder mixture; the metallic alloy amorphized after 5 hours milling indicating a good glass forming ability. In [8] Amorphous Ni59Zr20Ti16Sn5 alloys were fabricated by melt spinning and by mechanical alloying (MA) techniques. Differences in crystallization temperat[...]

Microstructure and properties of ball milled and hot compacted powder of 7055 aluminium alloy

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7xxx series (Al-Zn-Mg-Cu) aluminum alloys are widely used in the aircraft industry due to their low density, high strength and good workability [1, 2]. Their strengthening increases with the concentration of Zn and is associated with higher density of very fine precipitates of metastable η′-phase enriched with Zn and Mg. The high solute (about 8 wt. % of Zn) alloy designated AA 7055 (ALCOA) evokes the highest strength aluminium alloys produced by ingot metallurgy and is applied as upper wing skin materials in commercial aircraft [3]. The 7055 composition processed using the T77 temper provides a microstructure at and near grain boundaries that is resistant to both intergranular fracture and interglanular corrosion. Aluminium based materials produced by powder metallurgy (PM) processing offer a number of interesting opportunities for high strength applications. Powder metallurgy enables to fabricate high quality parts close to final dimensions with refined microstructure as compared with these produced by the conventional ingot metallurgy [4, 5]. The ball milling applied before the compaction allows obtaining a very fine microstructure and the extension of the solid solubility limits of the elements added to the alloy [6]. It results in improved mechanical and corrosion properties of the compacted products. PM technology provides more homogenous distribution of the precipitates and reduces the particle size that makes corrosion more uniform [7]. The aim of the present investigation was to study the effect of ball milling and hot pressing on the microstructure and properties of milled and compacted 7055 aluminium alloy powder. Exp erimental details The mixtures of elemental powders of aluminum, zinc, magnesium, copper and zirconium were used as starting materials to yield (wt. %) Al - 8% Zn - 2% - Mg - 2.3% Cu - 0.2% Zr compositions corresponding to 7055 commercial aluminium alloy. The ball milling of the powder was [...]


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W niniejszym artykule przedstawiono charakterystykę wiór aluminiowych pochodzących od jednego z producentów detali ze stopów aluminiowych, metody ich przeróbki dla uzyskania proszku oraz spieków. Materiały odpadowe w formie wiór aluminiowych poddano analizie składu chemicznego, składu ziarnowego i określeniu kształtu cząstek oraz badaniom wybranych własności technologicznych tj. gęstości nasypowej, gęstości nasypowej z usadem, sypkości, i zgęszczalności. Następnie wióra aluminiowe prasowano w zakresie ciśnień od 100 do 400 MPa i spiekano w piecu rurowym w temperaturach od 729 K(456 °C) do 801 K (528 °C) w czasie 30 min w atmosferze argonu. Ponadto część proszku prasowano na gorąco w próżni. Przeprowadzono badania gęstości, twardości i ilościowe charakterystyki porowatości spieków na bazie wiór aluminiowych. W celach porównawczych przedstawiono również charakterystykę granulek aluminiowych otrzymanych metodą rozpylania również pochodzących z recyklingu. Słowa kluczowe: materiały odpadowe, wióra aluminiowe, granulki aluminiowe, metalurgia proszków, proszki i spieki na osnowie aluminium CHARACTERISTICS OF WASTE METAL CHIPS FROM ALUMINUM ALLOYS AND A METHOD FOR MAKING POWDER AND SINTERS FROM THEM In the present paper composition and microstructure of aluminum alloys chips from production of aluminum alloy details, description of methods of powder preparation from chips and their sintering are presented. The chips were mechanically alloyed with aluminum powder to be further sintered. The chemical composition, distribution of particle size, the definition of particles shape and selected technological properties like: bulk density, tap density, flow and compressibility of powders were studied. Next, obtained aluminum alloy powders were compacted in the range of presses from 100 to 400 MPa and sintered in the tube furnace for 60 min in an argon gaseous envelope, at temperature from 729 K (456 °C) to 801 K Dr hab. inż. Joanna Karwan‐Baczews[...]

Impact of strain rate on Cu mechanical properties

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Materials with ultrafine-grained (UFG) structure have been studied in the last few years because of their unique properties. The main feature of UFG metals is grain size diameter which is below as 1 μm. Considering that grain size reduces to nanometer range, the materials exhibit unique mechanical and physical properties. They have high strength and wear resistance, good ductility at room temperature and superplasticity at elevated temperature [1, 2]. At the same time they have demonstrated properties as a decrease in the elastic moduli, the decrease of the Curie temperature, enhanced diffusivity and improved magnetic properties [1, 3, 4]. The severe plastic deformation methods have been applied to UFG materials formation. The ECAP, ECAP-BP, HPT, ARB are well known technologies nowadays and have been successfully used to structure formation with grain size ~70÷500 nm [5÷7]. The unique properties of UFG metals are connected with specific microstructures features. The UFG microstructure created during SPD processes is formed by dislocations arrangement - “dislocation cell structure“ having mostly low angle boundaries [8]. Based on Valiev’s study [1], during metal processing via SPD great amount of dislocations is introduced to material resulting in high level of internal stresses and elastic distortion of crystal lattice near a boundary. Consequently, the grains boundaries are in the non-equilibrium state and deformation mechanism as grain boundary sliding and grain rotation would be enhanced. The final UFG structure contains huge amount of grain boundaries with mainly high-angle misorientations [9]. The small grain size and great density of defects (as dislocations, vacancies, triple junctions) in UFG materials cause higher strength properties achievement. At the same time, some experimental results show occurrence of superplasticity at lower temperature as well as at high strain rate in UFG metals [10, 11[...]

The influence of the heat treatment on structure and properties of copper after DRECE process

  Several types of SPD technologies serving for production of UFG metals was developed already at the beginning of the nineties. One of them is new type of equipment DRECE (Dual Rolling Equal Channel Extrusion), designated for obtaining UFG structure in strip of sheet. Experiments with use of material Cu 99.5% were made on the DRECE machines in order to achieve grain refinement in the strip of sheet with dimensions 58x2x1000 mm. For orientation information, whether grain was refined preliminary metallographic analysis was made on optical microscope NEOPHOT 2. Structure was analysed on the surface in longitudinal direction in respect to direction of rolling, and also in cross section and longitudinal section. After DRECE machinery the annealing on part of extruded sheets was applied. Two procedure 400 and 450oC/15min/air were selected. Obecnie rozwinięte kilka technologii SPD przy wytwarzaniu metali UFG. Jedną z nich jest urządzenie DRECE (Dual Rolling Equal Channel Extrusion), opracowane w celu uzyskania struktury UFG w taśmach stalowych. Badania przy zastosowaniu miedzi 99,5% przeprowadzono na maszynie DRECE. Umożliwiło to rozdrobnienie ziarna w taśmach stalowych o wymiarach 58x2x1000 mm. W celu uzyskania informacji czy ziarno zo[...]

Mathematical simulation of deformation behaviour in Equal Channel Angular Rolling process

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During the last decade, fabrication of bulk nanostructured metals and alloys using severe plastic deformation (SPD) has been evolving as a rapidly progressing direction of modern materials science that is aimed at developing materials with new mechanical and functional properties for advanced application [1]. The principle of these developments is based on grain refinement down to the nanoscale level in bulk billets using SPD. Ultra-fine grained material produced by IPD are characterized by increased value of strength, fatigue properties and mechanical properties of superplasticity. These properties depend from nanosize grain structure, its distribution in the material, stress, texture and other structural properties. The authors [2] highlighted the important fact, that the evolution of structure during the IPD is not related to the transformation of the microstructure of UFG structure with high angled grain boundaries. After IPD using, nanosize structure polyhedral materials is achieved, by dislocations slides, or dislocations rotations inside grains and slides on grain boundaries [3, 4]. Various processes of intensive plastic deformations have been proposed for the process of drafting the UFG materials using a simple slip. The application of severe plastic deformation (SPD) to conventional polycrystalline metals provides a powerful tool for refine the grain size to the submicrometer or nanometer range [1]. Ultra-fine grained materials (UFG, grain size less than ~1 μm) with unique mechanical and physical properties can be produced by severe plastic deformation [5÷11], such as a noble technique called equal channel angular rolling (ECAR). Lee et al. [12] proposed that Φ can be adjusted from 100° to 140° for producing ultra-fine grains with high angles of mi[...]

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