GRAIN STRUCTURE AND BOUNDARY
DOE-HDBK-1017/1-93
Structure of Metals
Another important property of the grains is their orientation. Figure 4(a) represents a random
Figure 3 Grains and Boundaries
(a) Microscopic (b) Atomic
arrangement of the grains such that no one direction within the grains is aligned with the
external boundaries of the metal sample. This random orientation can be obtained by cross
rolling the material. If such a sample were rolled sufficiently in one direction, it might develop
a grain-oriented structure in the rolling direction as shown in Figure 4(b). This is called
preferred orientation. In many cases, preferred orientation is very desirable, but in other
instances, it can be most harmful. For example, preferred orientation in uranium fuel elements
can result in catastrophic changes in dimensions during use in a nuclear reactor.
Figure 4 Grain Orientation
(a) Random (b) Preferred
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