Mathematical Modelling of Bainite Transformation Kinetics

Abstract
Steels with a mixed microstructure of allotriomorphic ferrite, bainitic ferrite, retained austenite and martensite have potentially good combinations of high strength and formability. This work describes a kinetic theory for the formation of bainite in steels where the precipitation of carbides is suppressed. The theory is based on the mechanism of transformation. It includes, for example, a nucleation model based on the Magee/Olson/Cohen theory for martensite, growth by a diffusionless mechanism in which sheaves of bainite form by the repeated nucleation of sub-units. These latter platelets grow to a size limited by plastic accommodation of the shape deformation. The theory is compared against experimental data.