TEM OBSERVATION OF MICROSTRUCTURES AND FINE STRUCTURES DURING BAINITIC NUCLEATION IN THE STEEL 8Mn8SiMo
钢中贝氏体形核初期微观形貌及精细结构的TEM观察

The microstructure and substructure of the bainitic-ferrite at the most early stage of growth in an Fe-0.79C-8.3Mn-0.87St-0.50Mo steel are studied by TEM. It is observed that the bainite nuclei exhibit a thin plate morphology. And, the bainite formation has the character of catalysis nucleation by sub-units. Moreover, the existence of (lll)f defect plane is firstly observed, and its formation is considered to be the result of the plastic accommodation effect occurred in parent austenite during bainitic nucleation and growth. Defect planes, in fact, to be the glide plane of austenite matrix, consist of part of the bainitic-ferrite/austenite interface. Thus, the formation of bainitic-ferrite is of shear nature.