In Situ Observation on the Effects of Prior Martensite Formation on Nanostructured Low–Temperature Bainite Transformation

Nanobainite transformation behavior was comparably studied using in situ observations for two heat treatments: With and without partial quenching before isothermal holding at 300 °C. It was found that the prior martensite formation significantly accelerated the rate of the subsequent nanobainite transformation. Bainitic laths formed adjacent to a prior martensite plate and grew up to austenites. Bainite phase also formed both at the grain boundaries of the parent phase and inside the grains. Regarding the growth mode, bainite grows along the longitudinal direction and hardly grows along the lateral direction.