PINTO DA SILVA Elisabete Ghent University

Spoluautoři XU Wei, FÖJER Cecilia, HOUBAERT Yvan, SIETSMA Jilt, PETROV Roumen

The microstructural evolution of a low-carbon steel has been studied during the austenite decomposition, subsequent to initial martensite formation. Isothermal holding treatments after rapid cooling to various temperatures between martensite start (MS) and martensite finish (Mf) temperatures were carried out in a dilatometer with the intention to form controlled volume fractions of initial martensite and austenite. The purpose of the above heat treatments was to create conditions in which the phase transformations during isothermal treatment between the MS and Mf temperatures can take place. During the isothermal transformation specific complex microstructures consisting of bainite, martensite and retained austenite and carbides precipitation, depending on the holding temperature and time can be obtained. However, the nature of the isothermal transformations below MS is not completely understood and issues like the isothermal formation of martensite and bainite are still under discussion. In this study, the microstructure development was monitored by means of dilatometry and microstructural characterization of the transformation products by Scanning Electron Microscope, Electron Backscatter Diffraction and Transmission Electron Microscope. The results revealed that the resulting microstructures are mainly bainitic mixed with tempered martensite and carbides.