The ledge theory of recrystallization in polycrystalline metals

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Abstract
When a polycrystalline metal specimen is deformed, ledges must be produced on grain boundaries in the interior of the specimen, corresponding to dip lines on the external surface, but much less pronounced. During recrystallization, grain boundary migration occurs and a ledge would tend to straighten out so as to reduce the total energy by decreasing the area of grain boundary. If the volume swept by the migrating boundary remains stress free, and the height of the ledge is greater than a critical value dependent on the energy density in the deformed material, it is shown that the grain boundary will continue to migrate until the nucleus of a new grain capable of indefinite growth has been produced. The critical height h is given by h=0.1r=0.1 γ/E. where E is the energy density of the deformed materiel, γ is the grain boundary energy per unit area, and r is the equilibrium radius of curvature of the grain boundary between a recrystallized grain and the deformed matrix. On this basis it is shown that when a metal is cold-worked to a given strain, the temperature at which the metal is strained could have an effect on the grain size of the recrystallized specimen.

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