Grain growth behaviors during solution annealing based on the heterogeneous microstructure in hot rolled nuclear grade austenitic stainless steel.

• Heterogeneous microstructure was easily formed by DDRX during hot rolling. • Different storage energy can cause uneven grains during SA at high temperature. • Larger grains continued to annex adjacent smaller grains for the abnormal growth. • Adopting stepped heating from low to high temperatures can obtain uniform grains. Series of solution annealing experiments and quasi in-situ observation were employed to investigate the grain growth behaviors based on the heterogeneous microstructure with deformation bands and dynamic recrystallization (DRX) grains in hot rolled 316H austenitic stainless steel (ASS). It was worked out that during early stage of direct heating at high temperature of above 1000℃, the initial static recrystallized grains with different sizes would nucleate rapidly on the deformation band and DRX grains. With the extension of holding time, they gradually grew up to develop into the grains with large size differences, during which the larger grains continued to swallow adjacent smaller grains even presenting abnormal annexation or growth. However, by adopting stepped heating from low to high temperature, the grains evenly grew and presented relatively uniform distribution, which provides new idea for regulating grain size in manufacturing heavy ASSs. [ABSTRACT FROM AUTHOR]