ORIENTATION IMAGING MICROSCOPY - APPLICATION TO THE MEASUREMENT OF GRAIN-BOUNDARY STRUCTURE

The method of orientation imaging microscopy (OIM), which utilizes rap id. direct measurements of local lattice orientation on a grid of poin ts fixed upon flat surfaces sectioned from polycrystals, is described, and connected with established stereological theory. Examples of OIM applied to an Fe-2wt.%Si alloy are presented. Procedures associated wi th the S(V)/P(L) stereology are extended to obtain a new S(V)/f2 stere ology linking two-point statistics of lattice orientation with the dis tribution of grain boundary structure. The chief advantage of the new stereology is that it can be implemented directly from OIM. It is show n that the reliability of the method depends, not only on the number o f sectioned surfaces interrogated (as is the case with established S(V )/P(L) stereology), but also on the magnitude of the spacing between g rid points.