Abstract
Recently, procedures for recovering austenite fcc crystallographic information from EBSD (Electron Back-Scatter Diffraction) data recorded from martensite or other bcc transformation products have been proposed. Due to the difficulties in revealing prior austenite grain boundaries using available etching techniques, these reconstruction methods appear as promising tools for understanding austenite hot deformation behavior in low carbon steels. In a previous work, the accuracy of an in-house developed reconstruction code was validated using an Fe-30Ni alloy. Validation of this method in low carbon steels is more difficult due to the loss of austenitic orientation information. In addition, it is not known how the results of conventional metallography correlate with those of the reconstruction or which scan parameters or post-processing treatments are necessary for obtaining comparable results. To study this, two martensitic specimens obtained from water quenched recrystallized and deformed austenite were characterized in this study, using both conventional metallographic techniques and the above mentioned reconstruction procedure applied to EBSD scans acquired using different parameter values. The comparability of austenite grain size and morphology was analyzed as a function of the post-processing treatment. The results show that in order to obtain comparable results, it is critical to analyze the coherence of the twins present in the microstructure.
Highlights
In recent decades, the evolution of austenite microstructure during hot deformation in low carbon steels has been widely studied
Two martensitic specimens obtained from water quenched recrystallized and deformed austenite were characterized in this study, using both conventional metallographic techniques and the above mentioned reconstruction procedure applied to Electron Back-Scatter Diffraction (EBSD) scans acquired using different parameter values
The austenite morphology and grain size measurements obtained by applying conventional metallographic techniques to reveal the previous austenite grain boundaries from quenched martensite (Bechet-Beaujard etching) were compared with the results of a reconstruction procedure applied to orientation imaging data collected from the same martensitic specimens, quenched from both recrystallized and deformed austenite
Summary
The evolution of austenite microstructure during hot deformation in low carbon steels has been widely studied. Several etching techniques have been developed to reveal the austenite microstructure from quenched martensite [6,7], they are often ineffective, mainly in the case of low carbon steels [8]. Their ability to reveal some special grain boundaries is Metals 2018, 8, 294; doi:10.3390/met8050294 www.mdpi.com/journal/metals
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