Effect of cooling rate in variant selection during bainite transformation in heat affected zone of Cr-Mo steel

The effect of the cooling rate on the variant selection mechanism during bainite transformation was investigated in 2Cr- 1Mo steel. The specimen was heat treated to 1350 ℃ and held for 60s before being cooled to room temperature with various cooling rates. The usage of high temperature laser scanning confocal microscopy (LSCM) to heat and cool the specimen under controllable conditions enabled the bainite transformation to be observed in a real time. The heat treated sample was then analyzed by using electron backscattered diffraction (EBSD) method. As a result, increasing the cooling rate was discovered to refine the bainite block size. In the higher cooling rates, high angle variants were formed prominently.