The Dominant Factor of Competitive Grain Growth of the Nickel-Based Superalloys During Directional Solidification

The dominant factor of competitive grain growth was studied by trinary-crystal seeds during directional solidification. It was found that the grain overgrowth rate was weakly dependent on the temperature gradient when the misorientation angle of the misoriented grain was limited (£15°), which was inconsistent with the classical theoretical assumption that the grain overgrowth rate was determined by the difference of the tip undercooling between the competing grains. In contrast, the grain overgrowth rate was sensitive to the alloy composition. These phenomena were attributed to the mechanisms of solute interaction and sidebranching events, and the solute field was the dominant factor to govern the overgrowth behavior of the competing grains.