Abstract
Serrations develop in the grain boundaries (GB) of many metals and alloys as a result of local migrations to absorb dislocation walls. The serrations form only under deformation conditions where the subgrains reach about 2–10 μm in diameter; the conditions of temperature and strain rate depend on the metal and the effects of alloying on dynamic recovery. The small serrations evidently diminish GB sliding, making lattice deformation rate controlling. If the conditions are changed to produce lower strain rates, then initial serrations increase the creep life. In alloys with limited dynamic recovery, the serrations are also related to initiation of dynamic recrystallization, which is very important in preventing progression of GB cracking, and thus increasing the ductility in hot-forming operations. The formation of serrations or of a necklace of fine recrystallized grains along the GB of large grains (with good creep resistance) are noted for improving fatigue resistance.
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