Atoms in bainite, atomic mechanisms: APMS conference

A lecture given by Francisca Garcia Caballero, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. The atomic mechanism of the bainite transformation is discussed in the context of the highest resolution analytical experiments conceivable. The presentation file can be downloaded from

Abstract: After decades of debate on the mechanism for the formation of bainite, it is accepted that bainite grows via a displacive mechanism i.e., as plate-shaped transformation products exhibiting an invariant plane strain surface relief effect. But there is still much discussion on the diffusion or diffusionless nature of bainite. Elements of the theory are now routinely being used in the design of innovative steels and in the interpretation of a variety of experimental data. However, current experimental and theoretical understanding is limiting technological progress. The purpose of this atom probe tomography study was to track the atom distributions during the bainite reaction in steels with different carbon and silicon contents transformed over a wide range of temperatures (200-525 centigrade) to elucidate the role of reaction rate and diffusion in the formation of bainite with and without cementite precipitation. The results are providing new experimental evidence on subjects critically relevant to the understanding of the atomic mechanisms controlling bainitic ferrite formation, such as the incomplete transformation phenomenon, the carbon supersaturation of ferrite, the plastic accommodation of the surrounding austenite and cluster and carbides formation.

[feiyuzhao]

Another question is from this video, the To or To' is always believe that as the result of belence between the bainite-ferrite and retained austenite in carbon content, however in this video it is obvious that the carbon in austenite is more than the baintie-ferrite, it is still useful for calculating the To or the To is just suit for the boundry which have carbon in dislocation in same with retained austenite.

[feiyuzhao]

How the things happen between the To to Ae3, i mean the bainite plate growth during that time but still diffusionless (carbon not move)? How to discribe the plate growth ? just define as new bainite nuclear (sub-unit) ? but it is still need to diffusion the carbon during the nuclear process.