Two-Dimensional Observation of Grain Boundary Sliding of ODS Ferritic Steel in High Temperature Tension

High-temperature tensile deformation was performed using ODS ferritic steel, which has grain structure largely elongated and aligned in one direction, in the direction perpendicular to the grain axis. In the superplastic region II, two-dimensional grain boundary sliding (GBS) was achieved, in which the material did not shrink in the grain-axis direction and grain-boundary steps appeared only in the surface perpendicular to the grain axis. In this condition, a classical grain switching event was observed. Using kernel average misorientation maps drawn with SEM/EBSD, dominant deformation mechanisms and accommodation processes for GBS were examined in the different regions. Cooperative grain boundary sliding, in which only some of grain boundaries slide, was also observed