Effect of soluble particles on microstructural evolution during directional recrystallization.

How soluble particles affect microstructural evolution during directional recrystallization was studied in a Ni-12Al alloy containing two different sizes of Ni3Al particles. Ni-12Al with small particles can form columnar grains, but at a higher annealing temperature compared to its particle-free Ni-3Al counterpart, whilst columnar grains were not formed in Ni-12Al with large γ’ particles for the same annealing parameters. Columnar grains only formed after the γ’ particles dissolved. γ’ particle dissolution is not a trigger for columnar grain formation but is simply a prerequisite. Whether columnar grain can form or not was determined by the texture at the time of particle dissolution. If texture pinning exists after particle dissolution, abnormal grain growth occurs, and columnar grains form; if texture pinning is absent, columnar grains cannot form and normal grain growth occurs. How particles affect the columnar grain orientations, grain boundary character, and grain length/ width during directional recrystallization was also studied.