ANISOTHERMAL TRANSFORMATION OF AUSTENITE

The nucleation process in the pearlite range is additive, except that holding in the lower pearlite range it tends to accelerate subsequent reaction at high temperature. In the bainite range, holding at a high temperature retards subsequent nucleation at a low temperature, while holding at a low temperature appears to accelerate subsequent nuclea- tion at a high temperature. The deviation from additivity depends upon difference be- tween the temperatures involved and the holding duration. It is suggested that the embryo of bainite is the same as that of martensite, i. e., a b. c. c. region surrounded by a dislocation loop. Holding in the lower pearlite range accelerates subsequent transformation to bainite.