单晶合金激光熔凝过程中晶向对单晶完整性的影响

Effect of orientation on integrity of single crystal during laser melted single crystal

运用几何模型对单晶合金激光熔凝过程中激光扫描方向与[100]方向夹角ξ变化时熔池内的枝晶生长方向和速度进行了计算,研究了ξ增大时不同晶向区域的分布变化规律.发现随着ξ的增大,[010]区域增大,[010]区域减小,且熔池两边不同部分速度差别增强.根据速度变化规律,构造出了熔池不同部位的过冷区域变化图,说明了可能出现新晶粒的趋势变化,并与实验结果进行了比较,揭示了在晶向不同的交界区域产生新晶粒的内在机理.

The geometrical model is used to investigae the orientation of dendrite growth in a laser weld single crystal and the variation of the distribution of orientation zones when angle ξ between the laser scanning direction and the [100 ] orientation in （001） surface changes.With the increase of ξ,the [010]zone increases whereas the [010]zone shrinks.Meanwhile,the growth velocities of dendrite are different in different orientation zones inside the weld pool.The undercooling region is then constructed on the basis of the calculation results.It is found that the undercoolings are larger at the boundaries than in the grains for all orientation zones,which makes the boundaries vulnerable to the CET transition and production of the new grains.Moreover,with the increase of ξ,the abilities to form the new grains are different on the two sides of the weld pool.For comparison,the DD3 single crystals are laser welded and the experimental results are in good agree meent with theoretical ones.