Pre-martensite and bainite reactions: A thermal stability study
The comparative analysis of two ways to achieve ultra-fine bainitic steels considering isothermal heat treatment above and below martensite start (M) temperature was formulated. Although the presence of pre-martensite below the M temperature accelerates the nucleation time of the bainitic transforma...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/380109 |
| Acceso en línea: | http://hdl.handle.net/10261/380109 |
| Access Level: | acceso abierto |
| Palabra clave: | Medium carbon bainite Pre-martensite Retained austenite Tempered bainite Secondary hardening |
| Sumario: | The comparative analysis of two ways to achieve ultra-fine bainitic steels considering isothermal heat treatment above and below martensite start (M) temperature was formulated. Although the presence of pre-martensite below the M temperature accelerates the nucleation time of the bainitic transformation, the time to finish the transformation is longer (∼11.5 h) compared to the treatment above M (∼5 h). A qualitative and quantitative analysis of the morphology of the bainitic structure demonstrated that there are no significant differences in the thickness of the bainitic ferrite laths in both cases. However, a clear refinement of the retained austenite blocks of the steel treated below M was observed. Moreover, TEM and STEM/EDS studies revealed precipitation processes associated with the decomposition of the metastable bainitic and bainitic-martensitic structures during the tempering. It was shown that both heat treatment routes lead to secondary hardening during the tempering at 550 °C. At lower tempering temperatures, the bainitic matrix obtained above M was characterized by higher thermal stability, while the presence of pre-martensite in the steel treated below M has greater effectiveness in the secondary hardening effect at higher tempering temperatures and therefore in thermal stability of bainite at the high-temperature tempering range. These results provide a new perspective for designing heat treatment processes for advanced bainitic steels in applications subjected to operation at elevated temperatures. |
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