Combined reconstructive and displacive mechanisms involved in bainitic transformation

TEM observation and analysis have been conducted on bainitic transformation with and without the influence of externally applied tensile stress for alloyed steel 35MV7. Recrystallization was found to occur within the bainitic structures transformed at 450°C in cases of both with and without the application of external stress, and coupling between the reconstructive and displacive mechanisms is expected, due to the relatively high holding temperature and high dislocation density yielded with the displacive mechanism. Recrystallization was not observed within the bainitic structures transformed at lower temperature of 350°C, both with and without the application of stress. However, for the stressed specimen, the structure with very fine subgrains was found to be preserved and not reconstructed thermically, due to the low temperature and short holding time.