3D microstructure theories and techniques

Traditionally, materials scientists developed microstructure theories that relied on experimental quantities measured from planar sections. With the advent of 3D simulation of micro structures, and some recent advances in 3D characterization, this situation changed dramatically. Specifically, it is now possible, and desirable, to test microstructure theories with 3D data. Two theoretical aspects will be examined along with the measurements required to test them. First, a proposed extension is presented of Johnson-Mehl, Avrami, Kolmogorov theory to situations where phase domains are not randomly distributed. This requires measurement of the Gaussian curvature of the interphase interfaces, which may be extracted from the 3D microstructure. Such microstructural measurements are only available via characterization of 3D reconstructions or 3D theoretical representations. Next, a typical microstructure feature set will be described for a 3D polycrystalline network, using the topological and metrical properties of average N-hedra (ANHs). ANHs provide an average description of space-filling irregular polyhedral grains based on a theoretical set of generalized regular polyhedra.