Abstract
Microstructural and texture development with thermomechanical processing was performed through a combination of cold-rolling and annealing, in MA956 plate consisting of a layered and inhomogeneous microstructure. The alloy contained in mass percent, 20 Cr, 0.02C, 4.8 Al, 0.4 Ti, 0.4 Y2O3, and the balance iron. The starting material was as-hot-rolled plate, 9.7 mm thick. The as-hot-rolled plate was subjected to 40%, 60%, and 80% cold-rolling reduction and subsequently annealed at 1000°C, 1200°C, and 1380°C. Assessment of microstructural and texture developments before and after cold-rolling and annealing was performed using light optical microscopy (LOM), Vickers hardness testing, and electron backscatter diffraction (EBSD). Locally introduced misorientations by cold-rolling in each region were evaluated by Kernel Average Misorientation (KAM) maps. The as-hot-rolled condition contained a layered and inhomogeneous microstructure consisting of thin and coarse elongated grains, and aggregated regions which consisted of fine grains and sub-grains with {100} <011> texture. The microstructure of the 40% cold-rolled condition contained deformation bands, and the 60% and 80% cold-rolled conditions also contained highly deformed regions with intersecting deformation bands. The magnitude of KAM angles varied through the thickness depending on the initial microstructures. Recrystallization occurred in regions where high KAM angles were dense after annealing, and nucleation sites were fine elongated grain regions, deformation bands, and highly deformed regions. The shape and size of the recrystallized grains varied depending on the nucleation sites.
