CARACTERÍSTICAS DO ENCOURAMENTO DO AÇO TWIP ALTO Mn E BAIXO CARBONO LAMINADO A FRIO RECOZIDO
BEHAVIOR IN THE STRAIN HARDENING OF HIGH Mn AND LOW CARBON TWIP STEEL COLD ROLLING AND ANNEALING
Duarte, Dayanna Moreira; Ribeiro, Érica Aparecida S.; Dutra, Lorena Freitas; Gonzalez, Berenice Mendonça; Santos, Dagoberto Brandão
http://dx.doi.org/10.4322/tmm.00604008
Tecnol. Metal. Mater. Min., vol.6, n4, p.225-229, 2010
Resumo
Existe uma atual necessidade da indústria automobilística por materiais que combinem alta conformabilidade, alta resistência mecânica e baixo peso específico a fim de diminuir o consumo de combustíveis e aumentar a segurança dos passageiros. É neste contexto que surge o aço TWIP (TWinning Induced Plasticity), um aço de alto teor de manganês contendo silício e alumínio (2% a 4%) em sua composição. Sua principal característica é a formação de maclas sob ação de uma tensão. No presente trabalho, investiga-se como as características do encruamento de um aço C-0,06; Mn-25; Al-3; Si-2; Ni‑1, com efeito TWIP, laminado a quente e a frio e recozido a temperaturas variáveis entre 600°C e 850°C, influencia as suas propriedades mecânicas. Tal investigação consistiu na obtenção de micrografias ópticas e eletrônicas de varredura (MEV) e na avaliação do tamanho de grão e da fração volumétrica dos grãos recristalizados. Para complementação, foram realizados ensaios de tração. O estudo do encruamento teve a abordagem de Hollomon associada com o critério de Considère. A amostra recozida a 850°C apresenta um expoente de encruamento de 0,55, alongamento total de 66% e limite resistência de 700 MPa.
Palavras-chave
Efeito TWIP, Laminação a frio, Recristalização, Encruamento
Abstract
There is a current need for the automotive industry for materials that combine high formability, high strength and low specific weight in order to reduce fuel consumption and increase passenger safety. In this context, appears the TWIP steel (TWinning Induced Plasticity), defined as a steel with high content of manganese and, yet, silicon and aluminum (2% to 4%) in its composition. Its main feature is the formation of twining under stress. In this study, it was investigated how the characteristics of hardening work of the steel C-0,06, Mn-25, Al-3, Si-2, Ni-1, with TWIP effect, hot and cold rolling and annealing at temperatures varying between 600°C and 850°C, influences their mechanical properties. This research used optical micrography and scanning electron microscopy (SEM) for assessment of grain size and volume fraction of recrystallized grains. To complement this study, tensile tests were performed. The hardening work study uses the approach of Hollomon associated with the Considère criterion. The sample annealing to 850°C shows a work hardening exponent of 0.55, 66% of total elongation and maximum strength of 700 MPa.
Keywords
Effect TWIP, Cold rolling, Recrystallization, Strain hardening
References
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12 ZHANG, X. et al. Deformation microstructure of TRIP/TWIP Steels at the early deformation stages. In: ESOMAT 2009 - EUROPEAN SYMPOSIUM ON MARTENSITIC TRANSFORMATIONS, 8., Prague, Czech Republic. Proceedings... Disponível em:. Acesso em: 5 dez. 2009.
2 VERCAMMEN, S. et al. Cold rolling behavior of an austenitic Fe–30Mn–3Al–3Si TWIP-steel: the importance of deformation twinning. Acta Materialia, v. 52, n. 7, p. 2005-12, Apr. 2004.
3 FROMMEYER, G.; BRUX, U.; NEUMANN, P. Supra-ductile and high-strength manganese-TRIP/TWIP steels for high energy absorption purposes. ISIJ International, v. 43, n. 3, p. 438-46, Mar. 2003.
4 BOUAZIZ, O.; GUELTON, N. Modeling of TWIP effect on work-hardening. Materials Science and Engineering A, v. 319-21, p. 246-9, Dec. 2001.
5 ADLER, P. H.; OLSON, G. B.; OWEN, W. S. Strain hardening of hadfield manganese steel. Metallurgical Transactions, v. 17A, n. 10, p. 1725-37, Oct. 1986.
6 GRASSEL, O. et al. Phase transformation and mechanical properties of Fe–Mn–Si–Al TRIP-steels. Journal of Phyisique IV, v. 7, n. C5, p. 383-8, Nov. 1997.
7 RIOS, P. R. et al. Nucleation and growth during recrystallization. Materials Research, v. 8, n. 3, p. 225-38, Sep. 2005.
8 DUARTE, D. M.; RIBEIRO, E. A. S.; SANTOS, D. B. Comportamento mecânico do aço alto Mn e baixo C laminado a frio e recozido apresentando efeito TWIP. In: CONGRESSO DA ABM, 64., 2009, Belo Horizonte, MG. Anais… São Paulo: ABM, 2009. p. 1-10.
9 MI, Z. L. et al. Influence of cold rolling reduction on microstructure and mechanical properties of TWIP steel. Acta Metariallia, v. 20, n. 6, p. 441-7, Dec. 2007.
10 HUA, D. et al. Microstructures and mechanical properties of Fe-Mn-(Al, Si) TRIP/TWIP steels. Journal of Iron and Steel Research, v. 13, n. 6, p. 66-77, Nov. 2006.
11 DIETER, G. E. Mechanical metallurgy. Japan: McGraw-Hill Kogakusha, 1976. cap. 9, p. 329-74.
12 ZHANG, X. et al. Deformation microstructure of TRIP/TWIP Steels at the early deformation stages. In: ESOMAT 2009 - EUROPEAN SYMPOSIUM ON MARTENSITIC TRANSFORMATIONS, 8., Prague, Czech Republic. Proceedings... Disponível em:
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