An EBSP study of directionally recrystallized cold-rolled nickel

Electron backscattered patterns have been employed to reveal the orientation distribution and texture evolution of 90% cold-rolled polycrystalline nickel, which was subjected to directional annealing at a variety of temperatures. At 370 °C, equi-axed grain structures with a weak cube texture were observed after (primary) directional recrystallization at hot zone velocities from 2-40 mm/h, with the sharpest cube texture present at the slowest hot zone speed. At 1000 °C, with a temperature graduate of 50 °C/cm ahead of the hot zone, equi-axed grains with weak {1 2 4}<2 1 1¯> textures were produced by (secondary) directional recrystallization at hot zone velocities from 5-100 mm/h. In contrast, either columnar grains or single crystals could be produced by directional (secondary) recrystallization at either 1000 °C with a temperature gradient of 1000 °C/cm, or 800 °C with a temperature gradient of 800 °C/cm in front of the hot zone. The columnar grains also typically have {1 2 4}<2 1 1¯> orientations, the preferred texture for secondary recrystallization. The {1 2 4}<2 1 1¯>-oriented grains form high-angle, random boundaries, and thus, high-mobility boundaries with the texture-pinned, cube-oriented grains in front of the hot zone, suggesting that the columnar grains were produced by secondary recrystallization via oriented grain growth.