DD6合金选晶器定向凝固的数值模拟与实验

Numerical Simulation and Experimental Grain Selection of DD6 Superalloy in Spiral Grain Selector by Directional Solidification

使用有限元数值模拟和实验方法对DD6合金选晶器定向凝固过程的温度影响、晶粒组织以及晶粒生长进行了研究。结果表明,温度场模拟与选晶器定向凝固过程的温度变化基本相符,晶粒组织生长的模拟能够反映晶粒竞争生长的实际情况,与实验试样基本一致。由于取向与温度梯度不一致晶粒的位置被取代,使得引晶段中的晶粒平均半径随着高度增加而增大,晶粒密度不断减小,两者有负指数关系。对比了螺旋段不同高度截面EBSD晶粒取向实验成像与晶粒模拟结果,组织模拟与实验结果较为吻合。通过分析螺旋通道中的晶粒竞争生长关系,位于螺旋通道内侧和上部的晶粒更具有位置优势,容易被选晶器选出。

Spiral grain selector is a very important part of manufacturing process of single crystal blade, which is the key component of the aero-engine and industry gas turbine. Finite element simulation and experiments were used for researching the temperature effect of spiral grain selector, the grain structure and grain growth in the directional solidification process of DD6 superalloy. The results show that the simulation method can well predict the temperature change of directional solidification process, and the grain microstructure simulation is similar to the competitive growth of grains according to the experimental samples. The mean radius of grains increases with increasing height in the starter block, while the grain density declines since the location of the grain is replaced whose orientation is different from the direction of temperature gradient. The simulation results of grain morphology in the spiral part are consistent with experimental pictures from the EBSD orientation mapping technology. The grain is more advantageous to grow in the spiral part, which is located in the interior and upper part of the spiral channel longitudinal section.