Deformation Microstructure and Nucleation of Recrystallization in Hot-deformed Single Crystals of 18% Cr Ferritic Steel
Static recrystallization of the hot deformed single crystals with , ,  and  initial orientation of an 18% Cr ferritic stainless steel was studied. It was clarified that the hot-deformed microstructures and the recrystallization behaviors strongly depend on the initial orientation. The  crystal showed coarse and diffuse subgrains after hot-compression, the  and the  crystals formed relatively fine and uniform subgrains, and a number of the deformation bands elongated perpendicular to the compression axis developed in the  crystal. The  crystal was extremely hard to recrystallize and showed no recrystallization after a long time annealing. The  and the  crystals were relatively hard to recrystallize. The enhanced recrystallization along the deformation bands occurred in the  crystal, and the recrystallized grains had the orientations between those of the matrix and the deformation bands. The dislocation density, <I>i.e.</I>, the driving force for static recrystallization, in the hot-deformed subgrain structures were quantitatively evaluated on the basis of the detailed TEM observations. Although the dislocation density in the  crystal which showed no recrystallization was lower than those of the other orientations, that of the  crystal which showed enhanced nucleation was similar to that of the  crystal which was relatively hard to recrystallize. That is, the dislocation density in the deformed matrix does not necessarily correspond with the easiness of nucleation. EBSP measurements clearly showed that the narrow regions (transition bands) between the deformation bands and the matrix in the  crystal bear large misorientations about 50 degrees. It is concluded from those results that the large local misorientation in the deformation microstructure does be important for the nucleation of recrystallization and it is generally treacherous to discuss the nucleation problem only on the basis of the macroscopic and averaged information, such as the mean dislocation density, of the deformed state.
- ISIJ international
ISIJ international 38(4), 380-389, 1998-04-15
The Iron and Steel Institute of Japan