In order to study the
phase transformation mechanism of steel and to question the material science theory deeply,the method
of science and technology philosophy was used to analyze and discuss the self organization property of steel in this paper.The author thought that there were self organization function and
nonlinear interaction in the
phase transformation of steel.The self organization and its complexity were analyzed in the phase transformation mechanism and the microstructure and morphology of the pearlite decomposition,martensite transformation and bainite transformation in steel.It showed that the phase transformation mechanism is mono unit and the morphology of microstructure is multiple unit.The eutectoid decomposition is a self organization process,which is characterized by the integrated mechanism that ferrite and cementite acted as prevenient phase alternatively.At first,the martensite transformation induced structural fluctuation,which presented quasi martensite form.The fluctuation was enlarged by means of the movement of dislocation or fault.As a result,the original structure became unstable and a new structure was built,i.e.martensite crystal structure.The twin fluctuation was sure to form when the martensite transformation was achieved by means of twin shear strain.When the fluctuation was enlarged,the martensite crystal nucleus appeared in the form of twin crystal.The bainite transformation during the incubative period was inevitable to form carbon leant zones and carbon enriched zones through the fluctuation.The upper bainite and lower bainite have different transformation mechanism and kinetics curve respectively.In fact,the morphologies of all kinds of microstructure are diversiform.