ANÁLISE DO COMPORTAMENTO SOB EXTRUSÃO DE PÓS NANOESTRUTURADOS DE LIGAS DE ALUMÍNIO COMO UM PROCESSO TERMICAMENTE ATIVADO
EXTRUSION BEHAVIOUR ANALYSIS OF NANOSTRUCTURED ALUMINIUM POWDER ALLOYS UNDER A THERMALLY ACTIVATED PROCESS BASEMENT
Peres, Maurício Mhirdaui; Fogagnolo, João Batista; Kiminami, Claudio Shynti; Botta Filho, Walter José; Bolfarini, Claudemiro; Jorge Junior, Alberto Moreira
http://dx.doi.org/10.4322/tmm.00501002
Tecnol. Metal. Mater., vol.5, n1, p.6-11, 2008
Resumo
Neste trabalho, a extrusão de pós nanoestruturados é analisada a partir do ponto de vista de mecanismos de deformação ativados termicamente, tais como os que operam normalmente em materiais cristalinos convencionais. Pós nanoestruturados de ligas de alumínio foram conformadas por extrusão a quente em três temperaturas diferentes: 375°C, 400°C e 425°C, com razão de extrusão de 10:1 e velocidades de 1 mm/s, 15 mm/s e 30 mm/s. Os dados resultantes foram analisados utilizando equações típicas do trabalho a quente de materiais convencionais, principalmente a equação de Sellars, e os resultados são comparados com os dados da literatura de materiais convencionais processados por extrusão e torção a quente. Pode ser verificado que a extrusão a quente de materiais nanoestruturados também é um processo termicamente ativado, no qual o mecanismo controlador também é a escalagem ou o movimento severo de discordâncias. As mudanças microestruturais observadas são consistentes com os mecanismos de deformação propostos.
Palavras-chave
Extrusão, Pós, Alumínio, Energia de ativação
Abstract
In this work, the hot extrusion of nanostructured powders is analysed from the point of view of thermally activated deformation mechanisms, such as normally operate in conventional crystalline materials. Nanostructured aluminium powders alloy were deformed by hot extrusion at temperatures of 375°C, 400°C and to 425°C, with extrusion ratio of 10:1 and over the ram speed range of 1 mm/s to 30 mm/s. The resultant data were analyzed by means of typical equations from hot working of conventional materials, mainly the Sellars equation, and the results are compared with the literature data of conventional materials processed by hot extrusion and hot torsion. It is concluded that the hot extrusion of nanostructured materials is a thermally activated process, in which the rate-controlling mechanism is either the climb of edge dislocations or the motion of jogged screw dislocation. The microstructural changes observed are consistent with the proposed deformation mechanisms.
Keywords
Extrusion, Powders, Aluminum, Activation energy
References
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16 Nemat-Nasser, S. Introduction to high strain rate testing. In:__ASM HANDBOOK: Mechanical testing and evaluation. Metals Park : ASM, 2000. v. 8, p.939-41.
2 Fogagnolo, J.B.; Robert, M.H.; Ruiz-Navas, E.M.; Torralba, M. Extrusion of mechanically milled composite powders. Journal of Materials Science, v. 37, n. 21, p. 4603-7, Nov. 2002.
3 Onuh, S.O.; Ekoja, M.; Adeyemi, M.B. Effects of die geometry and extrusion speed on the cold extrusion of aluminium and lead alloys. Journal of Materials Processing and Technology, v. 132, n. 1-3, p. 274-85, Jan. 2003.
4 Ma, L.; Zahrah,T.F.; Fields, R. Processing and simulation of consolidation of amorphous aluminum-based powder material. In: IMECE’03: 2003 ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS, 2003, Washinton. Proceedings… Washington, D.C.: ASME, 2003. p. 15-21.
5 Kraft, F.F.; Powers, C. Optimizing extrusion through effective experimentation and analysis. In: INTERNATIONAL ALUMINUM EXTRUSION TECHNOLOGY SEMINAR, 7., 2000, Chicago. Proceedings… Chicago: Aluminum Association and the Aluminum Extruders Council, 2000. v 1, p. 43-9.
6 Thomsen, E.G.; Yang, C.T.; Kobayashi, S. Mechanics of plastic deformation in metal processing. New York: Macmillan 1965.
7 Castle, A.F.; Sheppard, T. Hot working theory applied to extrusion of some aluminum alloys. Metals Technology, v. 3, n. 10, p. 454-64, Oct. 1976.
8 Uvira, J.L.; Jonas, J.J. Hot compression of armco iron and silicon steel Transactions of the Metallurgical Society of AIME, v. 242, n. 8, p. 1619-26, Aug. 1968.
9 McQueen, H.J.; Jonas, J.J. Recovery and recrystallization during high temperature deformation. In: Herman, H. Treatise on materials science and technology. New York: Academic Press, 1975. p. 393-493.
10 Sherby, O.D.; Ruano, O.A. Rate-controlling processes in creep of subgrain containing aluminum materials. Materials Science and Engineering A, v. 410-1, p. 8-11, Nov. 2005.
11 Nabarro, F.R.N. Creep in commercially pure metals. Acta Materialia, v. 54, n. 2, p. 263-95, Jan. 2006.
12 Carmona, R.; Zhu, Q.; Sellars, C.M.; Beynon, J.H. Controlling mechanisms of deformation of AA5052 aluminium alloy at small strains under hot working conditions. Materials Science and Engineering A, v. 393, n. 1-2, p. 157-63, Feb. 2005.
13 Garofalo, F. An empirical relation refining the stress dependence of minimum creep rate in metals. Transaction of the Metallurgical Society of AIME, v. 227, n. 2, p. 351-6, Apr. 1963.
14 Sellars, C.M.; TEGARD, W.J.M. La relation entre la resistance et la structure dans la deformation a chaud. Mémories Scientifiques de la Revue Metallurgie, v. 63, n. 9, p.731-46, 1966.
15 McQueen, H.J.; Wong, W.A.; Jonas, J.J. Deformation of aluminum at high temperatures and strain rates. Canadian Journal of Physics, v. 45, n. 2, p.1225-34, Feb. 1967.
16 Nemat-Nasser, S. Introduction to high strain rate testing. In:__ASM HANDBOOK: Mechanical testing and evaluation. Metals Park : ASM, 2000. v. 8, p.939-41.
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