GRAIN STRUCTURE AND BOUNDARYDOE-HDBK-1017/1-93Structure of MetalsAnother important property of the grains is their orientation. Figure 4(a) represents a randomFigure 3 Grains and Boundaries(a) Microscopic (b) Atomicarrangement of the grains such that no one direction within the grains is aligned with theexternal boundaries of the metal sample. This random orientation can be obtained by crossrolling the material. If such a sample were rolled sufficiently in one direction, it might developa grain-oriented structure in the rolling direction as shown in Figure 4(b). This is calledpreferred orientation. In many cases, preferred orientation is very desirable, but in otherinstances, it can be most harmful. For example, preferred orientation in uranium fuel elementscan result in catastrophic changes in dimensions during use in a nuclear reactor.Figure 4 Grain Orientation(a) Random (b) PreferredMS-01Page 10Rev. 0
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