Analysis of grain misorientation distribution in polygonal ferrite of low-carbon steel

A method to deduce the origin and crystallographic features of the polycrystalline state basing on the analysis of misorientation distribution function is considered. According to this approach, the misorientation distribution is represented in the form of linear superposition of partial distributions, each distribution corresponding to the boundaries of a specific physical nature. Then the fractions of the boundaries of different types in the overall structure are determined from the best fit of the computed distribution to the experimental data. In the present work the method is applied to a low-carbon ferrite-pearlite steel. The emphasis is made on the boundaries, whose misorientations are predetermined by orientation relationship between parent austenite and ferrite, i.e. on the so-called crystallography-specified or inter-variant boundaries. It was shown that they constitute about one third of the total amount of boundaries in the polygonal ferrite microstructure.