Correlative microscopy of a carbide-free bainitic steel

Influence of Heat Treatment on Microstructure Stability and Mechanical Properties of a Carbide‐Free Bainitic Steel

“…However, it is interesting to note that additionally to the austenite fraction, also the amount of M‐A islands increases with increasing isothermal transformation temperature. Since the M‐A islands transform during the last cooling step to room temperature, they are highly dislocated and, therefore, decrease the quality of the Kikuchi diffraction patterns as apparent from the lower image quality (dark features indicated by arrows in Figure b and c) …”

“…This lower C concentration and, therefore, the lower thermodynamic stability explains the transformation of these areas to mainly C‐rich martensite upon cooling to room temperature. The outer regions of the M‐A islands remain preferentially partly austenitic, reflecting the C enrichment at the bainitic ferrite‐austenite interface.…”

“…Electron backscatter diffraction (EBSD) investigations were carried out after preparing the samples by electropolishing and a final manual polishing step according to ref., in order to prevent the transformation of the metastable retained austenite during preparation. The analyses were conducted in a field‐emission scanning electron microscope (SEM) VERSA 3D from FEI, which is equipped with a Hikari XP EBSD system from EDAX.…”

“…However, the austenite stability is not only influenced by its chemical composition, but also the combination of size, distribution and morphology, as well as the microstructure of the surrounding matrix and the resulting strength mismatch affect the austenite stability. Depending on the stability of the austenite, parts of it may transform to fresh martensite during quenching to room temperature, forming the so‐called martensite‐austenite (M‐A) islands . During plastic straining, the moderately stable retained austenite present at room temperature can transform to martensite through the transformation‐induced plasticity (TRIP) effect leading to an increase in the deformability.…”

Recent Developments of Crystallographic Analysis Methods in the Scanning Electron Microscope for Applications in Metallurgy

“…127,128 Furthermore, this technique has been utilized in the characterization of complex microstructures such as those resulting from high plastic deformation in flow formed Cr-Mo-V steel, the nano-sized cementite formation in quenched and tempered steel, and in the examination of carbide-free bainitic steels. [129][130][131] The use of TKD in tandem with EDS provides a tool able to collect simultaneous chemical information with high resolution, effectively limited by the sample thickness as in STEM. Brodusch et al first published the simultaneous acquisition of TKD and EDS maps in a single run, demonstrating the ability of TKD to identify phases and precipitates in compounds and alloys.…”