Microstructural Taxonomy

Microstructural taxonomy has reached a sufficient level of sophistication that it is possible to identify certain broad classes of microstructure. Before beginning, however, it is necessary to reiterate what this chapter is not. Our primary emphasis will be on metals. The majority of experimental data to be highlighted will be drawn from the metallurgical literature with occasional reference to nonmetallic precipitates within such metals. This is not to say that other material systems are without interesting microstructures. On the contrary, the subject is so vast as to have escaped even a modicum of competency on the part of the author. 

Microstructure in Single Phase Polycrystals. We begin with a discussion of the simplest microstructure (at least to characterize geometrically) in which the grain size is the dominant microstructural parameter. We are all used to the idea that the technologies that surround us are constrained by various codes which attempt to standardize products and the processes used to realize them. Such codes exist for everything ranging from skyscrapers to microwave ovens. It is 

The microstructure described above may be seen as the most homogeneous limit of those we will consider here. A complementary set of information concerning microstructures of the type featured above can be obtained by mapping the orientations of the various grains making up the polycrystal. The basic idea is that one may determine the preponderance of different crystal orientations. The new technique of orientation imaging microscopy now allows for the determination of such orientational information with high spatial resolution. An example of the type of results that are obtained via this technique is shown in fig. 10.3. 

Precipitates and Inclusions. The presence of more than a single species in a material makes it possible that a given microstructure will be far richer than that described above. In particular, by virtue of the presence of several species coupled 

As the figures indicate, the most naive theoretical intuition is incomplete. Below we will take up the challenge of how to explain the origins and characteristics of these microstructures. In addition, in chap. 11, we will examine the way in which a distribution of second-phase particles can alter the mechanical properties of a material. 

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