A METHOD FOR EVALUATION OF UNIFORMITY IN GRAIN-STRUCTURE

Concept of uniformity on microstructure of materials has been clarifie d. On this basis, uniformity on grain structure has been understood as size uniformity, representing the distribution of grain size, and spa tial uniformity, expressing the degree of clustering of similar-sized grains. Indices of uniformity, U-size and U-sp have been proposed: Siz e uniformity, U-size is designated by the inverse of the geometric sta ndard deviation for grain intersect area, a, sigma(ga). Spatial unifor mity, U-sp for the square object area of side length, L is expressed b y the deviation of a microstructural center of gravity from a simple c enter as follows. U-sp=1-root 2[(x(G)-x(S))(2)+(y(G)-y(S))(2)])(1/2)/L , where, the simple center G(x(G), y(G)) is the center of gravity for the whole object structure, and the microstructural center Gs(x(S), y( S)) is the center weighted by the intersect area of each grain. U-sp d epends on setting a standard length, L; the ways of setting are one co rresponding to mean grain size and another of representing an absolute value. Further, it has confirmed that the evaluation of uniformity is useful to the actural microstructures of pure iron samples.