Efeito da temperatura e do tempo de austêmpera na microestrutura e no comportamento mecânico de aços TRIP
Effect of austempering temperature and time on the microstructure and the mechanical behavior of TRIP steels
Maria Clara Michel Marinho; Eduardo Antônio Pinto Dias; Aline Silva Magalhães; Wellington Lopes; Elaine Carballo Siqueira Correa
Resumo
O desenvolvimento, ao longo das últimas décadas, de aços, como os assistidos pelo efeito TRIP (Transformation Induced Plasticity), que possuem boa conformabilidade, elevada resistência mecânica e relativamente baixo custo, foi uma das formas de atender ao mercado automobilístico que necessita de materiais cada vez mais leves e com elevado nível de segurança. Tais características podem ser obtidas a partir de ciclos térmicos e/ou termomecânicos diversos, sendo atribuídas à microestrutura multiconstituída desses aços e, principalmente, ao fenômeno de transformação da austenita em martensita por deformação plástica. Nesse contexto, o objetivo deste trabalho foi analisar os efeitos de parâmetros do ciclo térmico na microestrutura e nas propriedades de um aço com médio teor de carbono. Foi observado que a elevação do tempo de austêmpera aumentou a proporção de bainita e de austenita retida, assim como do teor de carbono nessa última fase, resultando na diminuição da resistência mecânica e na elevação da ductilidade e do expoente de encruamento do aço. De modo análogo, o aumento da temperatura de austêmpera resultou na redução da resistência mecânica, aumento da ductilidade e do expoente de encruamento.
Palavras-chave
Abstract
The development of metallic alloys, such as TRIP (Transformation Induced Plasticity) assisted steels, which exhibit good formability, high mechanical strength and relatively low cost, has been one way to meet the automotive industry demands for lighter and safer materials. These characteristics, achieved through various thermal and/or thermomechanical treatments, are due to the multiphase microstructure of these steels and, primarily, to the transformation of retained austenite into martensite induced by plastic deformation. In this context, the aim of this work was to analyze the effects of parameters of the thermal cycle on the microstructure and mechanical properties of a low carbon steel. It was observed that an increase in the austempering time led to an increase in the proportion of bainite and retained austenite, as well as the carbon content of the latter, resulting in a decrease in hardness and mechanical strength, and an increase in the ductility and the strain hardening exponent of the steel. Similarly, an increase in the austempering temperature resulted in a reduction in mechanical strength and hardness, and an increase in ductility and strain hardening exponent.
Keywords
Referências
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Submetido em:
14/07/2023
Aceito em:
18/07/2024
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