Assessing the scale contributing factors of three carbide-free bainitic steels: A complementary theoretical and experimental approach

Future Trends on Displacive Stress and Strain Induced Transformations in Steels

“…The reduction of sheaves affects the number of blocks of austenite that are present in the microstructure, i.e., microstructures show less blocky γ if they have been transformed under the effect of stress [145]. To the best knowledge of the authors, the effect of the stress on the thickness of the α B has not been assessed, although it would be expected that microstructures are refined because of the increase of driving force [146][147][148], σ Y (in the case σ Y is overcome) [146][147][148], and transformation kinetics [149]. It has been reported, though, that applying stress while a specimen is isothermally treated promoted the coalescence of α B plates [150].…”

“…In multiphase structures, the α B SIT/DIT at temperatures higher than room temperature have been reported in few studies [2][3][4]19,29], although their effect on the mechanical properties or the differences with respect to the SIT/DIT taking place in fully austenitic structures has not been discussed. Further research would be needed in order to know if the conclusions made with the α and ε transformations could be extrapolated to α B transformations, although some differences are expected, such as: (a) while the martensite transformation can be spontaneous, the bainitic transformation is thermally activated, which may inhibit the SIT/DIT in some extent; (b) while martensite transformation does not lead to any carbon partition, carbon is partitioned from α B after a plate/lath is fully grown, which is expected to increase the SFE [151,152] and the driving force for the transformation [149], inhibiting the SIT/DIT in a higher extent as the transformation progresses [153]; (c) bainitic ferrite may not be as hard as martensite because of their different carbon contents, hence, the α B TRIP effect may not lead to such a pronounced strengthening as the α TRIP.…”

Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction

“…In contrast, the network of structures in the deformed sample seems to be more preferentially oriented perpendicularly to the loading direction (as indicated by dashed rectangles). Considering that a significant amount of bainitic ferrite (46 Mass.%) was induced by strain, combined with the fact that plastic deformation during phase transformation alters the average scale of the microstructure [4,8], it seems plausible to suggest that the microstructure develops perpendicular to the compression during DT (γ→αb) .…”

“…Although the thermomechanical processing of advanced bainitic steels has received considerable attention recently [1][2][3][4][5][6][7][8], knowledge on the dynamic transformation of austenite to bainite (in the present work referred as "DT (γ→αb) ") is limited. This non-conventional path for bainitic transformation was only evidenced by deviations in the stress-strain curves during ausforming experiments usually below 500 • C [3,4,8,9]. So far, the DT (γ→αb) understanding is unclear in terms of kinetics, changes in lattice parameter, partitioning behavior of alloying elements, and the attainable volume fraction of bainitic ferrite during the deformation cycle.…”

Effect of prior martensite formation on the bainite transformation kinetics in high-strength 3% Mn multiphase steel

“…The thickness of bainite laths depends on the chemical composition of steel and heat treatment parameters. These factors affect the driving force for bainitic transformation and eventual stabilization of retained austenite [4][5][6][7]. The ultra-fine bainitic microstructure is usually obtained via isothermal treatment at a temperature about 300 °C, above martensite start temperature (M s ).…”