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

The method of orientation imaging microscopy (OIM), which utilizes rapid. direct measurements of local lattice orientation on a grid of points 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 with the S(V)/P(L) stereology are extended to obtain a new S(V)/f2 stereology linking two-point statistics of lattice orientation with the distribution of grain boundary structure. The chief advantage of the new stereology is that it can be implemented directly from OIM. It is shown that the reliability of the method depends, not only on the number of sectioned surfaces interrogated (as is the case with established S(V)/P(L) stereology), but also on the magnitude of the spacing between grid points.