Kinetics, Solute-Drag and Mechanism of the Bainite Reaction in Steels

H. K. D. H. Bhadeshia

Abstract

The mechanism of bainite growth in steel is investigated by comparing traditional ideas with high-resolution experimental data. Imaging-atom-probe studies demonstrate that substitutional solutes do not segregate at the interface, thereby disproving the solute-drag theory and the local equilibrium model. Furthermore, direct observations via photo-emission electron microscopy reveal that bainite sub-units expand at speeds significantly faster than those predicted by carbon diffusion control under paraequilibrium conditions. The findings suggest that bainite forms through a shear-based mechanism rather than through long-range atom redistribution. Ultimately, the work leads to the conclusion that conventional theories regarding equilibrium and solute-induced drag are insufficient to explain the kinetic reality of the bainite reaction.

Proceedings of an International Conference on Phase Transformations in Ferrous Alloys,
Philadelphia, A.I.M.E., eds A. R. Marder and J. I. Goldstein, 1984, pp. 335-340

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