THE ROLE OF AUSFORMING ON PHASE TRANSFORMATION KINETICS OF NANOBAINITE DURING CONTINUOUS COOLING TRANSFORMATION

In this paper, the effects of ausforming on phase transformation kinetics and development of microstructure during the continuous cooling transformation of nanobainite were examined by dilatometry, metallographic method, and X-ray diffraction. The dilatometric analysis was done via Gleeble 3800-GTC to determine the suitable heat treatment procedure. Samples were continuous cooled at different rates to investigate the cooling rate suitable for bainitic transformation. Among various cooling rates 0.03°C/s was found to be suitable for nanobainite transformation as it avoids the formation of martensite and pearlite. The Combination of continuous cooling at 0.03°C/s and deformation with strain rate of 0%, 20% and 30% at 500°C increases volume fraction of bainite from 67% to 79%. Phase transformation kinetics of nanobainite due to ausforming followed by continuous cooling was found to be increased due to the dislocation debris generated by the plastic deformation which acts as nucleating sites for bainite.