Ultra-fine ferrite formation during deformation of undercooled austenite in a low carbon steel

Based on the theory of deformation enhanced transformation, ultra-fine ferrite structure with grain size of about 2 mum was formed during deformation of undercooled austenite between A(3)-Ar-3. Two mechanisms are involved during the deformation process: deformation-enhanced transformation is the dominated factor in the early stage of deformation, while ferrite dynamic recrystallization plays a major role in the final stage after deformation enhanced austenite to ferrite transformation nearly completed. Deformation enhanced transformation is. a nuleation dominated process, which is the main mechanism of grain refinement. Ferrite grains nucleate at austenite grain boundary and, areas with high density defect under small strain, then form repeatedly at areas with high stored energy in front of the ferrite/austenite interface.