Grain-Boundary Migration and Grain Growth

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Abstract
The principles of grain growth are reviewed and grain-boundary migration is discussed in this context. The specification of the driving force for grain growth on the basis of microstructural parameters is one of the central problems in grain-growth kinetics. The approaches that have been proposed are outlined and consideration is given to the pinning effects which reduce the effective driving force below that specified by the geometry of the grain structure. The grain-boundary mobility is discussed in terms of its reciprocal, the velocity-independent drag. It is noted that this drag is made up of an intrinsic component and a solute-dependent component, which, in combination, can result in the non-linear Arrhenius grain-growth relationships reported in the literature. The continuing and unresolved question of the role of the orientation relationships specifying a high-angle boundary upon its migration characteristics are discussed, and reference is made to some new observations in this area. The final section concerns itself with the consequences of deviations from normal grain-growth behaviour upon the character of the structures developed, and includes abnormal grain growth and the role of abnormalities in the primary recrystallization structure upon subsequent grain-growth characteristics.