Transmission Electron Microscope Observation of the Bainite of Carbon Steel

Abstract

The structure of the bainite in a 0.7% carbon steel has been studied by means of transmission electron microscopy and selected-area electron diffraction. The lower bainite consists of ferrite grains with internal fine cementite precipitates lying on one kind of planes (probably stacking fault planes). This behaviour of cementite is different from that of the tempered martensite, and moreover in the ferrite there are hardly seen any traces of the twin faults which are usually found in the martensite. On the other hand, in the upper bainite, the cementite plate is large and situated by the ferrite plate which contains a large number of dislocations. The electron diffraction patterns show that both the upper and lower bainites have nearly the same orientation relationships between the ferrite and the cementite. That is, Referring to these results and the habit of the precipitated cementite, the formation mechanism of the bainite is discussed in connection with the martensite transformation.

In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

“…The axes of these carbides were inclined between 53 • and 62 • to the growth direction of the bainitic ferrite. It has been reported that the angle between carbides in the lower bainite ferrite inclines at about 60 • to the growth direction of ferrite, which is very close to the angles measured in the present investigation [30]. It should also be noted that in agreement with reported results in the literature, the morphology of decomposed retained austenite blocks is very similar to that of lower bainite [31].…”

Modelling Upper and Lower Bainite Trasformation in Steels

“…The diameter L q in aB is, then, given by: It is reported that cementite within bainitic ferrite has orientation relationship with bainitic ferrite. 19,20) This is caused by decreasing the interfacial energy, which is dealt as one of fitting parameters in this model.…”

Effects of the Austenite Grain Size and Deformation in the Unrecrystallized Austenite Region on Bainite Transformation Behavior and Microstructure.

“…From the viewpoint of the industrial development of bainite steel, transformation behavior under continuous cooling conditions needs to be clarified. However only little has been studied with respect to the effects of these factors mentioned above under continuous cooling conditions.6) Two different models, diffusional7-9) and displacive mechanisms, [10][11][12] Relationship between the hardness of transformed products and the 50 '/* transformation temperature in steel 2.…”