The effect of plastic deformation on the austenite-to-ferrite phase transformation in low-alloy steel

The accelerating effect of plastic deformation of austenite on the austenite-ferrite transformation can be attributed to three mechanisms: (i) a higher driving force for nucleation, (ii) an increased driving force for growth, (iii) an enhanced nucleation potency due to a larger internal surface area and changes in the grain boundary character. The first two are primarily related to the stored energy, the latter to the deformation geometry and the effect of deformation on the structure of grain boundaries. It is yet unclear which mechanism prevails. By applying specific combinations of strain and strain rate. the stored energy can be made the same during different tests, while the deformation geometry varies. In this way, insight is gained in the relative importance of the three mechanisms on the phase-transformation kinetics and the resulting microstructure.