THE INFLUENCE OF THERMOMECHANICAL TREATMENT ON THE TRANSFORMATION BEHAVIOR OF STEELS

The effect of thermomechanical treatment on the gamma - alpha-transfor mation in steel has been reviewed. It has been shown that the thermome chanically conditioned austenite significantly influences the kinetics of transformation due to the differences in the formation of product phases. An enhanced nucleation during the diffusion controlled transfo rmation, as a result of austenite grain refinement and/or austenite st rengthening, leads to a substantial refinement of the microstructure ( ferrite grains, pearlite nodules). The deformation substructure of aus tenite may strongly affect the shear mechanism of the diffusionless tr ansformation, which leads to finely fragmented martensite crystals. Su ch differences in the transformation characteristics result in differe nt formation temperatures of transformation products and so to the cha nges in CCT diagrams.