Mechanical stability of retained austenite during plastic deformation of super high strength carbide free bainitic steels
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New carbide free bainitic microstructures are gaining an increasing interest on behalf the scientific and industrial community. The excellent combination of mechanical properties achieved in those microstructures with no need of complex heat treatments or thermomechanical processes represents their main advantage. The strength is mainly achieved by means of the very fine bainitic ferrite plates, consequence of the transformation mechanism, but the parameters contributing to the ductility of those microstructures are still unclear in this type of microstructures, where a soft phase, retained austenite, is imbibed in a very strong matrix of bainitic ferrite. A priori is reasonable to assume that retained austenite will control the levels of ductility achieved. Further enhancement of ductility can be achieved by the transformation of retained austenite into martensite (strain or stress assisted), thus its mechanical stability plays an important role in the final ductility. In this study, by means of X-ray analysis of interrupted compression tests, it is studied the influence that different microstructural aspects of retained austenite may have on its mechanical stability.
KeywordsFerrite Austenite Martensite Bainite Bainitic Ferrite
The authors gratefully acknowledge the support of Spanish Ministerio de Ciencia y Tecnología Plan Nacional de I_D_I (2004–2007) funding this research under the contract MAT2007–63873. All of us want to thank to T. Iung and S. Allain (ARCELOR RESEARCH) for manufacturing the designed alloys. We are also extremely grateful to M. J. Santofimia for her contribution to the design and development of these alloys and to M. Arias Ruiz de Larramendi for preliminary mechanical tests performed in these alloys.
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