Analysis of transformation plasticity during bainitic transformation under externally applied stress

Abstract

A computational model is proposed to calculate the transformation strain of bainitic transformation in steel under an external stress. To evaluate the difference of nucleation rates among the bainitic variants within a parent austenite grain, the mechanical interaction energy between the lattice deformation of each variant and the applied external stress is considered based on the Kurdjurnov-Sachs (KS) orientation relationship and the concept of variant selectivity. The calculated results are then compared with the experimental dilatometric data for the isothermal and non-isothermal bainitic transformations under various uniaxial compressive stresses. The calculated transformation strain was found to be in good agreement with the experimental values, suggesting that a change in the variant selectivity to accommodate the externally applied stress would induce permanent strain after bainitic transformation.