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1

Innovative approach to uniform imprint of micron and submicron features

Hocheng H., Wen T. T.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 1

79-82

EN

Purpose: To develop methods for uniform imprint of micron and submicron-scale features. Design/methodology/approach: The first is gas-assisted imprint technique. In use of gas to exert isotropic pressure in hot embossing, uniform embossing throughout the area is achieved. Another approach is the electromagnetic force-assisted imprinting technology, which employs the electromagnetic force to pull the magnetic stamp with submicron-scale structures into a UV-curable resist on the substrate. The liquid photopolymer is then cured by UV-irradiation at room temperature. Furthermore, the ferromagnetic UV-curable material is made of nano-Fe powder and UV-curable polymer. The micron and submicron-scale magnetic features can be fabricated. Findings: Uniform embossing throughout the area is achieved. Under the condition of 180°C, 40kgf/cm² and 90 seconds, high quality and uniformity of micro-optical components can be fabricated. For electromagnetic force-assisted imprinting technology, a large area of sub-micron pattern with a line width of 502nm and a pitch of 1µm can be successfully fabricated under the condition of pressure of 1.6kgf/cm² for 30 seconds and UV curing for 0.5 minute. Using ferromagnetic UV-curable resist, the structures can be successfully fabricated under the pressure of 0.92kgf/cm² with the same UV-curable time. These results indicate good uniformity and controllability on both the gas-assisted hot embossing and electromagnetic force-assisted imprinting for efficient fabrication of micron- or submicron-scale structures. Practical implications: The facilities have been designed, constructed and tested. The effects of processing parameters including the processing temperature, pressure, and time on the replication quality were investigated. Originality/value: There are advantages of high uniformity, low pressure and low temperature for various applications in micron and sub-micron features and other micro-optical components such as gratings and waveguides etc.

2

Experimental methods of metal forming

Groger M., Cizek L., Hernas A.

Hutnik, Wiadomości Hutnicze

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2008

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Vol. 75, nr 5

235-242

EN

Methods of severe plastic deformation should meet a number of requirements which are to be taken into account while developing them for formation of nanostructures in bulk samples and billets. These requirements are as follows. Firstly, it is important to obtain ultra fine-grained structures with prevailing high-angle grain boundaries since only in this case can a qualitative change in properties of materials occur. Secondly, the formation of nanostructures uniform within the whole volume of a sample is necessary for providing stable properties of the processed materials. Thirdly, though samples are exposed to large plastic deformations they should not have any mechanical damage or cracks. Traditional methods of severe plastic deformation, such as rolling, drawing or extrusion cannot meet these requirements. Formation of nanostructures in bulk samples is impossible without application of special mechanical schemes of deformation providing large deformations at relatively low temperatures as well as without determination of optimal regimes of material processing. At present the majority of the obtained results are connected with application of equal channel angular pressing There are known some investigations on formation of nano- and submicrocrystalline structures in various metals and alloys by means of multiple forging. The present section is devoted to the questions of realization of the SPD methods mentioned above, their modelling and optimal regimes. Data on evolution of initial microstructure and its transformation to a nanostructured state during severe plastic deformation are also considered here.

PL

W artykule dokonano przeglądu nowoczesnych metod kształtowania metali zmierzających do formowania nanostruktury oraz ultradrobnoziarnistej struktury metali, zapewniających odpowiedni stopień oraz jednorodność przerobu i tym samym uzyskanie jednorodnych własności w całej objętości odkształcanego metalu. Podczas kształtowania nanostruktur w masowych próbkach i kęsach należy uwzględnić szereg uwarunkowań zarówno teoretycznych jak i technologicznych. Po pierwsze, ważne jest uzyskanie ultra-drobnoziarnisty eh struktur z dominującymi szerokokątowymi granicami ziarn. Po drugie, kształtowanie nanostruktur jednorodnych w całej objętości próbki jest konieczne, aby zapewnić stabilne i jednorodne właściwości obrabianych materiałów Po trzecie materiały poddane dużym odkształceniom plastycznym, nie powinny mieć żadnych wad mechanicznych lub pęknięć

3

Microstructure and texture development in Ag-Cu alloys subjected to severe plastic deformation

Prusko P., Adamczyk-Cieślak B., Mizera J.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 1

199-206

EN

In this work, modification of microstructure and texture development in Ag and Ag-Cu system alloys (Ag — 4% wt. Cu, Ag — 12% wt. Cu) subjected to Severe Plastic Deformation (SPD) was analysed. Rods of 15 mm diameter were the starting material for the experiment, they were obtained with the extrusion-torsion (ET) method. Next, the rods were subject to deformation by hydrostatic extrusion (HE) (E = 3.2) and 3 times subjected to Equal Channel Angular Pressing (ECAP) — ε = 3.4. As a result of the tests performed, it was found out that the alloys examined, subjected to SPD, displayed a high refinement of the microstructure, which led to a significant improvement of mechanical properties. The microstructure of materials produced by SPD strongly depends on the technological parameters of deformation. In the initial state (ET deformation) all of the alloys exhibited a fibrous character of texture. A similar fibrous texture characteristic was also found after HE, whereas after the ECAP the initial texture was completely changed. In all methods of deformation, the Ag sample shows a very strong texture comparison to Ag — 4% wt. Cu and Ag — 12% wt. Cu.

PL

W niniejszej pracy dokonano zmian mikrostruktury i tekstury w stopach z układu Ag — Cu (Ag — 4% wg. Cu, Ag — 12% wg. Cu) oraz w czystym srebrze po dużym odkształceniu plastycznym. Pręty w stanie wyjściowym o średnicy 15 mm uzyskano poprzez zastosowanie wyciskania ze skręcaniem wlewków o średnicy 50 mm. Następnie poddano dużemu odkształceniu plastycznemu przez zagięty kanal kątowy (ε = 3.4). Przeprowadzone badania wykazały znaczne rozdrobnienie mikrostruktury stopów poddanych SPD w odniesieniu do stanu wyjściowego. Charakter otrzymanej mikrostruktury jest silnie uzależniony od rodzaju zastosowanej metody odkształcenia. W stanie wyjściowym wszystkie badane materiały wykazywały osiowy charakter tekstury. Podobnie sytuacja wyglądała w przypadku wyciskania hydrostatycznego, jednakże metoda ECAP spowodowala calkowitą zmianę charakteru tekstury w odniesieniu do stanu wyjściowego. Po wszystkich metodach odkształcania stwierdzono ponadto, że próbki wykonane z czystego srebra wykazują silniejszą teksturę w odniesieniu do próbek Ag — 4% wg. Cu oraz Ag — 12% wg. Cu.

4

Odkształcalność kompozytów aluminiowych wzmocnionych popiołami lotnymi

Richert J., Leszczyńska B., Galanty M., Mroczkowski M., Tkaczewski P.

Rudy i Metale Nieżelazne

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2007

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R. 52, nr 11

656-664

PL

Przedstawiono badania nad odkształcalnością kompozytu otrzymanego metodą prasowania na zimno proszku aluminiowego zmieszanego z 30 % objętością popiołów lotnych. Sprasowany kompozyt ma niekorzystną strukturę. Cechuje się znaczną porowatością i niskimi siłami spójności pomiędzy cząstkami aluminium, stykającymi się ze sobą. Z tego względu taki materiał kompozytowy jest bardzo kruchy. Uplastycznienie kruchych materiałów jest możliwe przede wszystkim przy zastosowaniu specjalnych procesów odkształcania plastycznego na gorąco, które odznaczają się wysokim ciśnieniem hydrostatycznym. W celu uzyskania wysokojakościowego kompozytu zamiast spiekania zastosowano niekonwencjonalny proces, polegający na ściskaniu kompozytu umieszczonego we wnętrzu grubościennego pierścienia, wykonanego z duraluminium. Specjalny, wyjściowy zestaw materiałowy ściskano na prasie hydraulicznej w temperaturze 450 °C ze stopniem odkształcenia, wynoszącym 50 %. Na podstawie przeprowadzonych badań mikroskopowych stwierdzono, że przyjęty proces odkształcenia plastycznego na gorąco zapewnia bardzo korzystną strukturę kompozytu. Poza tym doświadczalnie wykazano, że dzięki utworzeniu takiej struktury możliwe jest przeprowadzenie dalszych odkształceń plastycznych, na przykład za pomocą procesów ściskania oraz walcowania na zimno.

EN

The investigations of the deformability of aluminium matrix composite were introduced in the article. This composite was obtained by cold pressing the aluminium powder mixed with 30 % volume of fly ashes. Compressed composite has the unfavourable structure. This structure characterizes considerable porosity and the low strengths of cohesion among the aluminium particles, touching with each other. From this regard such composite material is very brittle. The plasticization of brittle materials is possible first of all by the use of the special processes of a hot plastic deforming, which they are distinguish by the high hydrostatical pressure. Instead of sintering the unconventional process was applied to get high-quality composite. The composite was placed in interior the duraluminium ring, and it was compressed on a hydraulic press in temperature of 450 °C with the plastic strain degree of 50 %. On the basis of conducted microscopic investigations, it has been stated that the applied process of the plastic deformation assured the very advantageous structure of composite. Besides, it was showed experimentally that formation such structure allows on realization further plastic deformations, for example by use of the cold compression and rolling processes.

5

Elasto-plastic models of polycrystalline material deformation and their applications

Wierzbanowski K., Baczmański A., Lipiński P., Lodini A.

Archives of Metallurgy and Materials

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2007

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Vol. 52, iss. 1

77-86

EN

Then elasto-plastic models, used for analysis of polycrystalline material deformation are presented and discussed. Two models are presented in details: the Leffers-Wierzbanowski model and the elasto-plastic self-consistent model, developed by Lipinski, Berveiller and Zaoui. The crystallographic mechanisms of plastic deformation, being the basis of the models, are evoked. The both models have many common elements, they differ, however, in the type of assumed grain-matrix interaction. Some current applications of the decribed models are shown. They are e.g.: prediction of deformation textures, stress-strain curves and distribution of the stored energy as well as the interpretation of residual stress measurement by diffraction technique.

PL

W pracy przedstawiono podstawowe modele typu sprężysto-plastycznego, używane do opisu odkształcenia materiałów polikrystalicznych. Omówiono w szczegółach dwa modele: model Leffersa-Wierzbanowskiego oraz sprężysto-plastyczny model samo-uzgodniony, opracowany przez Lipińskiego, Berveillera i Zaoui. Scharakteryzowano mechanizmy krystalograficzne odkształcenia plastycznego, leżące u podstaw modeli. Oba modele mają wiele wspólnych elementów, róznią się one jednak typem założonego oddziaływania pomiędzy ziarnem i otaczającym go materiałem. Pokazano kilka najczęstszych zastosowań omówionych modeli. Są nimi np.: przewidywanie tekstur odkształcenia, makroskopowych krzywych umocnienia oraz rozkładu energii zgromadzonej w materiale jak również interpretacja dyfrakcyjnych badań naprężeń wewnętrznych.

6

Microstructure of ultrafine-grained Al produced by severe plastic deformation

Rodak K., Pawlicki J.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 7

409-412

EN

Purpose: The structure of Al subjected to severe plastic deformation by means of compression with oscillatory torsion and by combined method (compression followed by compression with oscillatory torsion) were investigated. Design/methodology/approach: Al samples were deformed at torsion frequency (f) changed from 0 Hz (compression) to 1.6 Hz under a constant torsion angle (α) ≈ 6° and compression speed (v)=0.1mm/s. For combined methods the samples were compressed for strain ε = 0.7 and next deformed at mentioned parameters of compression with oscillatory torsion. Structural investigations were conducted by using light microscopy (LM) and transmission electron microscopy (TEM). Findings: The structural analysis made by TEM shows that the processing by compression with oscillatory torsion ensures obtaining a structure (at selected parameters) with a mean grain size ≈ 1.6 µm. Combined methods of deformation lead to grain refinement to about ≈ 0.9µm moreover material with uniform ultra-fine grained (UFG) microstructure was obtained. Research limitations/implications: The understanding in refinement of Al structure could help to modify the process and design deformation parameters. Practical implications: The knowledge of the characteristic features of unconventionally deformed materials will provide the usefulness of the employed method to produce materials having the desirable functional properties. Originality/value: Oscillatory compression is a deformation procedure applied to achieve large strains. However there is no studies on evolution of the microstructures during deformation by using mentioned mode. This paper provides these information's.

7

Microstructural refinement of Al before compression with oscillatory torsion process

Rodak K.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 6

357-360

EN

Purpose: The present study is aimed at a quantitative description of microstructural parameters as a average subgrain size, subgrain width and length of Al deformed by using compression test at ε=0.8 with the next annealing. Conventional compression followed by annealing as a preliminary stage for compression with oscillatory torsion should contribute to refining grain size. Design/methodology/approach: Al samples were compressed in room temperature to a true strain of 0.8 and next annealed at 250 °C for 1 min and 1h. Structural investigations were conducted by using light microscopy (LM) and transmission electron microscopy (TEM). Findings: Compression leads to the formation of elongated subgrains bounded by microbands. The average subgrain size increase steadily with annealing time. The aspect ratio (R) of the grain length and the grain width is high initially especially for the as compressed materials and decreasing significantly after annealing. On annealing the deformed material, dislocation recovery occurs, leading to reductions in dislocation density both at grain boundaries and within the grains. Some of the dislocations arrange to form small eqiuaxed subboundaries. Research limitations/implications: An increase of the contribution of grain boundary (by using method of preliminary refining structure of Al) to the deformation process by compression with oscillatory torsion may influence on more refining Al structure than compression with oscillatory torsion only. Originality/value: Contributes to research on deformation procedure to achieve a refine structure of metals.