Microstructure characterization and dynamic recrystallization in an Alloy 800H

The nucleation mechanism of dynamic recrystallization of an austenitic steel Alloy 800H at intermediate temperatures (900, 950, 1000 and 1050°C) and strain rates from 10−1 s−1 to 10−3 s−1 was studied by transmission electron microscopy (TEM). It is found that dynamic recrystallization (DRX) starts in the region of grain boundaries without bulging. Detailed investigations show that the development of the microstructure is highly inhomogeneous, consisting of dense dislocation walls and microbands in which dynamic recrystallization occurred near the grain boundaries due to an orientation gradient. Correlation between microstructural evolution and nucleation mechanism is analysed on the basis of substructure observations and measurements.