| Abstract Scope |
When highly pure Ni powder compacts with a size of 180 micron were annealed at 550⁰C, abnormal grains with {100} facets formed, grew, and impinged upon each other. All the boundaries were dry with no liquid film. The {100} grain boundary planes were singular with atomic steps and had a lower energy than the other planes. This result indicates that grain growth in Ni is governed by the movement of {100} singular planes with step formation and spreading. With increasing annealing temperature, the fraction of faceted boundaries decreased. For a fixed time period and increasing temperature, the grain growth behavior changed from primary stagnant to primary abnormal with well-faceted cubic grains, secondary stagnant, secondary abnormal with apparently rounded grains and quite normal. This repetitive grain growth behavior with temperature increase can be a critical support for our mixed mechanism principle of microstructural evolution, which was deduced a decade ago. |