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Microstructure and properties of α + β brass after ECAP processing

Dutkiewicz J., Masdeu F., Malczewski P., Kukuła A.

Archives of Materials Science and Engineering

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2009

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Vol. 39, nr 2

80-83

EN

Purpose: Purpose of this paper is to determine the effect of Equal Channel Angular Pressing (ECAP) processing on the microstructure and hardness of α + β ?brasses. The effect of deformation temperature and number of passes was investigated particularly on the shape and size of grains of both phases. Design/methodology/approach: The specially constructed channel with 90° pressing angle, allowing heating of the tool with the sample was used for ECAP processing. The grain size was investigated using optical and transmission electron microscopy. The hardness and measurements microhardness were used to determine the effect of ECAP on the hardness of both phases. Findings: Significant grain refinement down to 300 nm from the initial 20 mm was observed after ECAP processing at 300°C. At 400°C grain refinement occurred down to 1-3 mm. Frequent microtwins were observed within aphase. The microhardness of the αphase was higher than that of αphase, 235 HV and 173 HV respectively. Research limitations/implications: The limitation is a size of the sample which makes difficult future applications. Another one is elevated temperature (minimum 300°C) otherwise the samples forms crack. This limits also the grain refinement which is above the range of nanomaterials. Practical implications: Significant grain refinement allows to increase the hardness and strength of the sample preserving a good plasticity. The limitation is the size of the channel what limits the application. The material could be used in such cases when high strength of brasses is needed with sufficient plasticity and good conductivity. Originality/value: In this paper detailed TEM studies were performed for α + β brasses showing high density of microtwins and higher density of dislocations within ? phase, than in the bphase. Higher hardness of the bphase results from the ordering, which hinder deformation of this phase.

2

Ultrafine grain formation during equal channel angular extrusion in an Al-Mg-Si alloy

Greger M., Kocich R., Čížek L., Kander L.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 15, nr 1-2

181--185

EN

Purpose: The possibility of including a new methods into classical technologies is one of reasons which for writing this paper. Design/methodology/approach: Microstructural development of aluminium alloy 6082 during equal-channel angular pressing (ECAP). Analysis of structure was made by light microscopy and SEM analysis. Findings: This procedure makes it possible to obtain after 4 passes the grain size of approx. 1 μm. In order to obtain an optimum micro-structure it is necessary to apply more passes with turning of the sample between individual passes by 90° about the longitudinal axis. Research limitations/implications: In this process (ECAP) was one of head problems a impossibility of application other shapes material. One of eventuality solving in respect thereof is using DECAP process. Practical implications: Radii of rounding of working edges of extruding channel must correspond to conditions for laminar flow of metal. Originality/value: Aluminium alloy 6082 was used to ECAP process, and found to be that this material can to change substructure structure, mechanical properties, respectively. Achieved quality level of mechanical properties is a function of number of passes as well as used technological route.

3

The experience at extrusion of the magnesium alloy MgAl9Zn1 by the equal channel angular pressing

Greger M., Jonšta Z., Widomská M., Kocich R.

Elektronika : konstrukcje, technologie, zastosowania

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2004

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Vol. 45, nr 8-9

172-174

EN

Method of equal channel angular pressing is used for obtaining of new properties of metallic materials. Extrusion of magnesium alloy of the type MgAl9Zn1 has been verified experimentally with focus on acquisition of basic findings about behaviour of material flow in extrusion channel, about magnitude of deformation resistance, deformability and structural changes in extruded piece. The results of experiments have been described and compared with the values obtained and normal direct extrusion. Practical use of the method ECAP consists in possibilities of obtaining a fine-grain structure in extruded pieces and to make use of it at subsequent super-plastic forming.

PL

Metoda prasowania kątowego o jednakowych kanałach wykorzystywana jest w celu uzyskania nowych właściwości materiałów metalicznych. Wyciskanie stopu magnezowego typu MgAl9Zn1 zostało zweryfikowane doświadczalnie. Skupiono się przy tym na akwizycji podstawowych danych o zachowaniu się materiału podczas płynięcia w kanale do wyciskania, odporności na odkształcanie, podatności na odkształcenie oraz zmianach strukturalnych w wyciskanym elemencie. W artykule opisano rezultaty tych eksperymentów, a także porównano je z wartościami uzyskanymi przy normalnym bezpośrednim wyciskaniu. Praktyczna użyteczność metody prasowania kątowego o jednakowych kanałach polega na możliwości uzyskania w wyciskanych elementach struktury drobnoziarnistej oraz na wykorzystaniu tego podczas następującego po nim kształtowania nadplastycznego.