Study On The Pearlite Isothermal Transformation And Crystallographic Analysis Of Multiphase Microstructure With EBSD

This work is divided into two parts. One is as the earlier stage of the comparative study of magnetic field on isothermal pearlitic phase transformation above eutectoid temperature. Isothermal pearlitic phase and circular processing on 50Si2Mn3 cast steel under conventional conditions had been carried out without the field. In addition, trial samples for the comparative study had been supplied. The influences of the isothermal temperatures, isothermal processing time and isothermal loop processing on the microstructures of these specimens have been observed and analyzed. The experimental results confirmed to general phase transformation principle under conventional conditions, that is:(1) The circulation processing can effectively promote the granulation process of lamellar pearlite; (2) The magnetic circulation processing at 710? (above the eutectoid temperature) can induce pearlite.The other one is the study on crystalline information of multiphase for experimental casting steel. The result has indicated that calibration rate of electron backscatter pattern (EBSP) has a great relationship with the transformed volume fraction of magnetic-induced pearlite (MIP), the more the fraction, the high the calibration rate of EBSP, thus, a better reflection of the distribution, crystallographic orientation and structure of MIP colonies can be achieved with the data collected through area scanning; At quite early stage of phase transformation, the low transformed fraction of MIP will give a low calibration rate of EBSP over the surface of sample, the crystallographic data collected by point analysis on a ferrite plate in a pearlite colony can be used to represent qualitatively the crystallographic orientation of the pearlite colony, therefore, micro-texture information of MIP over the surface of polycrystalline sample might be obtained from a large number of specific measurements. It has also indicated that a pearlite colony can be formed by the multi-nucleation mechanism,those discontinuous precipitated particles along the prior austenite grain boundaries are ferrite.