单晶高温合金叶片定向凝固过程数值模拟

Numerical Simulation of Directional Solidification Process of Single Crystal Superalloy Blade

基于有限元建立了单晶高温合金叶片定向凝固过程的数理模型,对3.6、4.5、7.2 mm/min等3种抽拉速度下的温度场、温度梯度、冷却速率进行了数值模拟。模拟计算结果显示,抽拉速度为7.2 mm/min时,叶片糊状区较宽,等温线倾斜程度比3.6 mm/min和4.5 mm/min时更大。随抽拉速度提高,固-液界面的温度梯度降低,选晶器内螺旋内、外侧温度梯度相差较大。起晶器和选晶器起始段中的冷却速率不受抽拉速度的影响;螺旋后段与叶身随抽拉速度增加,冷却速率增大。将温度场计算结果与CAFé模块耦合,对形核生长情况进行模拟,研究了抽拉速度对杂晶缺陷形成的影响。结果显示,抽拉速度为7.2 mm/min时,在缘板边缘处易形成杂晶;抽拉速度为3.6 mm/min和4.8 mm/min时,形成了完整的单晶。

The mathematical model of the directional solidification process of single crystal superalloy blade was established based on the finite element method.The temperature field,temperature gradient and cooling rate were simulated at different with drawal rates.The results indicate that when the with drawal rate is 7.2 mm/min,the mushy zone of the blade is wider,and the isotherm inclination is greater than that of 3.6 mm/min and 4.5 mm/min.With the withdrawal rate increasing,the temperature gradient G_(L) of the solid-liquid interface is decreased,and the temperature gradient on the inside of the spiral is larger than that on the outside.The withdrawal rate has little effect on the cooling rate in the starter block of grain selector and blade,while the cooling rate in the back block is increased with the withdrawal rate increase.Meanwhile,the nucleation and growth were simulated by coupling the temperature field and CAFé module to investigate the effect of withdrawal rate on the stray grains formation.The results reveal that stray grains are generated at the edge of the platform when the withdrawal rate is 7.2 mm/min,and the complete single crystal are generated when withdrawal rate is 3.6 mm/min or 4.8 mm/min.