采用SCN--1.7%Eth(质量分数)透明模型合金, 应用自制的晶粒择优取向角度可控的透明模型合金双籽晶试样盒, 对定向凝固中双晶竞争生长的微观组织演化进行了实时观察, 研究了二维条件下, 抽拉速率和晶粒取向对发散晶粒竞争淘汰的影响. 结果表明, 对于发散双晶, 随抽拉速率的提高, 择优取向晶粒淘汰非择优取向晶粒的速度变慢, 其主要原因在于, 抽拉速率增大会减小一次枝晶间距并降低择优取向晶粒一次臂新增频率; 当择优取向晶粒优先生长方向与热流方向不完全一致时, 在特定抽拉速率下, 择优取向晶粒由于受到型壁的制约, 最终亦可能被淘汰.

Grain selection in directional solidification is a fundamental process in single-crystal super alloy production. In fact, many factors can influence this process. This work only focuses on the effect of pulling rates on competitive divergence in directional solidification. The competitive growth of bi-crystal atdifferent pulling rates was observed during 2D directional solidification using the transparent model alloy SCN-1.7%Eth (mass fraction). The results show that as the pulling rate increases, it becomes harder for preferred grain to eliminate slant grain. This is because the increase of pulling rate decreases primary dendrite arm spacing and slightly reduces the frequency of new primary dendrite arms. When the growth direction of preferred grain is not well aligned with temperature gradient, the preferred grain can also be eliminated by the slant grain at specific pulling rates.