Effect of solute on microstructural evolution during directional recrystallization

Abstract

Ni-3at. % Al was directionally annealed at different annealing temperatures and drawing velocities to reveal how solute affects the microstructural evolution during directional recrystallization. Compared to high-purity Ni, Ni-3at. % Al has a reduced upper limit for the drawing velocity that can form columnar grains, which can be explained by solute drag. It was found out solute drag effect was not only misorientation angle dependent but also misorientation rotation axis dependent, which narrowed the mobility difference of different misorientation high-angle boundaries. As a result, the boundaries between columnar grains and the small equiaxed grains ahead of them have a near- random distribution instead of a defined rotation relationship, and, thus, columnar grains can arise from random textures instead of arising from a single texture. This leads to a relatively high percent of high-angle columnar grain boundaries in the random columnar grain boundaries. Solute also lowers the stacking fault energy, which leads to a larger fraction of both island grains and columnar grain boundaries that are twin boundaries compared to high-purity nickel.