Theoretical Analysis of Duplex-Grain Structure

Abstract

There has been no method to distinguish exactly and conveniently whether materials are composed of grains of uniform size or grains of mixed sizes.The authors analysed theoretically the size and its distribution of the grains appeared on a sectional plain of the material and presented a method for that purpose, and then experimentally comfirmed this method to be suitable one.
According to the authors'calculation, when the material are composed of grains of uniform size, on a sectional plain of the material, the percentage.of area (R), occupied by grains having the area ranged from the area of large circle of the grain to its 75%, must be nearly 70%.Then if the measured value is nearly 70%, the material may be defined to be composed of grains of uniform size, and, if not, grains of mixed sizes.
Experimental results indicates that the above consideration is correct, i.e., the measured value of R on a sample of carbon steel, which is confirmed to be duplex-grain structure by three dimensional measurment, is only a few percent.