Three-dimensional Distribution of Grain Structure and Image Analysis

Abstract

The aim of this research is to establish a stereological method to characterize three-dimensional (3-D) distribution of grains in a metal from its sectional images with an application of the current image processing techniques. First of all, 3-D models of metals consisting of homogeneous grains and duplex grains were generated by simulating the processes of nucleation and crystallization with various nucleus distributions and growth rates. The frequency distribution of cut-lengths of the ASTM or JSPS standard chart of austenite (No. 7 or 8) obtained by cutting them with equiinterval parallel lines comes into a normal distribution. It was confirmed that there is no significant difference between the standard chart and the homogeneous grain model by statistical tests, and relations among mean cut-length, grain size number, mean diameter and mean volume were derived on the homogeneous grain. For duplex grains, formulae were derived to calculate the degree of duplication and the fraction of volume occupied by different sizes of grains from the distribution of duplex grains.
The results can practically be utilized to obtain 3-D information about homogeneous and duplex grain structures with image processing techniques.