镍基单晶高温合金螺旋选晶过程的数值模拟

Simulation of Grain Selection during Solidification of Ni base Single Crystal Superalloy in Spiral Grain Selector

采用ProCAST&CAFE模型,模拟了选晶法制备镍基单晶高温合金DD3过程中的晶粒组织演化。结果表明,选晶器引晶段的主要作用是优化晶粒取向,随着距引晶段底部距离的增加,<001>晶向与热流方向偏离角较大的晶粒逐渐被淘汰,到达距引晶段底部26 mm处时,<001>取向的晶粒与热流方向之间的夹角平均值小于10°。螺旋选晶段的主要作用是获得单一晶粒,其对晶粒的取向没有优化作用。螺旋选晶过程中,靠近螺旋通道外侧的晶粒因受到螺旋通道较强的几何阻碍逐渐失去生长空间,而靠近螺旋通道内侧的晶粒通常被选为最终的单晶。螺旋选晶段对晶粒的选择或淘汰与该晶粒在螺旋通道内所处的位置(螺旋通道的内侧或外侧)有密切关系,而与晶粒的晶体学取向没有必然联系。

Grain texture evolution during the directional solidification of Ni-base single crystal superalloy DD3 in spiral selector has been simulated by ProCAST＆CAFE model. The results indicate that the main function of starter block is to optimize the grain orientations. The favorably 〈001〉 oriented grains would overgrow the unfavorable grains with increasing of the distance from the base of starter block, and when the distance is up to 26 mm, the average deviation of the grain orientations is controlled within 10°. Only one grain is allowed to grow into the cast by grain selecting in the spiral part, and no optimization occurs during grain orientation selection in the spiral. The grains near the outer wall of the spiral passage are always geometrically blocked by the spiral passage, and the grain near the inner wall of the spiral passage is usually selected as the final single crystal. It obviously depends on the location of the grains and has no apparent connection to the orientation of the grains whether the grains are selected or blocked in the spiral passage.