The grain growth behavior in 316L stainless steel have been investigated in relation to grain boundary structure transformations. Grain boundary structure changes with annealing temperature, which may give another possibility to interpret grain growth behavior in polycrystalline materials.
316L stainless steel specimens are annealed under Ar atmosphere at 1100 deg,1200 deg and 1300 deg where no precipitation is observed. The internal microstructures and the grain size distributions of the specimens annealed at 1100 deg show the abnormal grain growth (AGG) behavior, while those at 1200 deg, 1300 deg show the normal grain growth (NGG) behavior. It is suggested that some non-linear relationships between driving force and migration rate exist in ordered grain boundaries (ordered grain boundary structure can be introduced by lowering heat-treatment temperature) and lead to AGG. For verification, two stage heat-treatments, step-up and step-down, are performed. It seems that the size advantage or the recrystallization texture is not sufficient to trigger AGG, and there should be ordering of grain boundary structures.
As a evidence, TEM micrographs of faceted non-twin boundaries are presented; faceted boundaries are expected to have ordered structures. Faceted non-twin boundaries are found in the specimens annealed at 1100 deg where AGG occurs, while all of the boundaries have smooth and curved shapes at 1300 deg except twin boundaries.