Effect of deformation on the bainitic transformation
Résumé
The effect of deformation on the growth kinetics of bainitic ferrite plates was investigated under two types of
conditions. In the first, deformation (ausforming) precedes the austenite-to-bainite transformation, while in the
second case the phase transformation and deformation occur concurrently. The results clearly demonstrate that
ausforming accelerates the nucleation of bainitic ferrite plates, leading to significant refinement of the final
microstructure. When the bainite transformation takes place during deformation, the effect on nucleation was
less obvious, but a clear increase in the growth rate of bainitic ferrite was observed. A modified version of the
Zener-Hillert model for plate growth, with adjustments that allow for incorporating the effect of defects in the
matrix and the effect of applied deformation on the movement of interfacial disconnections, was used to
rationalize the effect of deformation on the growth kinetics. The calculations show that after ausforming, the
stored dislocations act as a barrier to the growth of bainitic ferrite plates, resulting in a decreased lengthening
rate. Conversely, when the transformation occurs concurrently with deformation, the lengthening rate of bainitic
ferrite plates is accelerated due to the interaction between the applied stress and the disconnections at the tip of
the bainitic ferrite plates
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