Research On The Formation Characteristics And The Formation Mode Of The Nanostructured Bainite In Steel

In this paper,the intermediate temperature products of the experimental steel with Fe-0.89C-1.36Si-1.01Cr-0.43Mn(wt.%)have been investigated by X-ray diffraction phase analysis,optical microscope observation,EPMA composition determination,HRTEM structure analysis and the calculation of first principles.The formation characteristics and microstructure state of nanostructured bainite have been studied.The formation mode of nanostructured bainite has been discussed.It was found that austenitization at the range of 880°C~950°C is the appropriate heat treatment condition to obtain nanostructured bainite for the experimental steel.In the early stages,a subunit of the nanostructured bainite formed firsly.Continuously generated subunits form a bainite ferrite strip by head-tail manner.The distortion zone caused by di-vacancies is mainly the characteristic of the nanostructured bainite.There is no lattice atom clustering phenomenon(such as Fe atoms)in a subunit of the nanostructured bainite.The divacancies combinations formed during high temperature austenitization induce the nucleation of the subunits of the nanostructured bainite and the growth of the sheave-like morphology.Nanostructured bainite has nano size characteristics,but its atomic arrangement and lattice distribution state is different from general nanocrystalline.