晶体取向对定向凝固枝晶生长的影响

采用类金属透明模型合金丁二腈-1.0 wt%乙醇(SCN-1.0 wt% Eth)合金, 考察了晶体取向对定向凝固过程中晶粒的平界面失稳孕育时间、枝晶形态演化以及枝晶一次间距的影响. 结果表明, 随着枝晶择优生长方向与温度梯度方向夹角的增大, 晶粒的平界面失稳孕育时间增加, 界面的稳定性增强; 对于不同晶体取向的枝晶形态演化, 枝晶择优生长方向与温度梯度方向夹角越大, 枝晶二次臂不对称生长越严重, 同时, 具有生长优势的枝晶二次臂对相邻枝晶的生长的抑制越强烈; 至于不同晶体取向的枝晶一次间距, 随着枝晶择优生长方向与温度梯度方向夹角的增大, 枝晶一次间距增大. 关键词： 定向凝固 平界面失稳 枝晶间距 晶体取向

Effect of crystallographic orientation on dendrite growth in directional solidification

Dendrite is a typical pattern in directional solidification, attracting many theoretical and experimental researches. However, the effect of crystallographic orientation on dendrite growth is less considered in these researches. In this paper, using a transparent model alloy SCN-1.0 wt% Eth, the effects of crystallographic orientation on the incubation time of planar interface instability, the dendritical morphological feature, and the primary dendrite spacing in directional solidification are investigated. Three crystal grains with different angles between the dendrite axis direction and thermal gradient direction are chosen in our experimental. The experimental results show that the incubation time of planar interface instability increases with the deviation of dendrite axis from thermal gradient direction, which suggests that the deviation of dendrite axis favors the planar interface stability. And with the increase of deviation angle of dendrite axis, the side branches of dendrite become more asymmetric and the preferred side-branches suppress neighboring dendrite growth. Also it is found that the primary dendrite spacing becomes larger as the angle between the dendrite axis direction and thermal gradient direction increases.
Keywords： diretional solidification planar interface instability dendrite spacing crystallographic orientation