改进元胞自动机法数值模拟高温合金凝固过程枝晶生长行为

提出了一种改进元胞自动机方法,该法充分考虑了溶质场和热扩散对枝晶生长的作用,并基于溶质场方程的27点离散格式,对多元高温合金凝固时的枝晶生长行为进行了数值模拟和试验对比,研究了枝晶生长形貌演变和单晶叶片铸件杂晶形成规律。结果表明:增大过冷度能促进枝晶快速生长,但由于溶质富集,单晶粒枝晶尖端生长速率随时间延长而逐渐减小;当冷却速率较低时,铸件等截面区域偏离热流取向的枝晶会淘汰与热流取向相同的枝晶;在定向凝固枝晶生长中,等温线内凹温度场中的变截面区域易形成杂晶;上述模拟计算结果和试验结果及相关文献的研究结果一致,该改进元胞自动机方法具有一定的有效性和实用性。

Numerical Simulation of Dendritic Growth Behavior in Solidification of Superalloy by an Improved Cellular Automaton Method

An improved cellular automata method,fully considering the combined effect of solute field and thermal diffusion on dendrite growth,was proposed.Based on the 27-point discrete scheme of solute field equation,the numerical simulation of the dendritic growth behavior in multi-element superalloy solidification was carried out and compared with the experimental results.The dendritic growth morphology evolution and the stray grain formation in single crystal blade casting were studied.The results show that increasing the undercooling degree could promote the dendritic growth,but the growth rate of the single crystal dendrite tip gradually decreased with time due to solute enrichment.At low cooling rates,dendrites deviating from the heat flow direction eliminated dendrites with the same orientation as the heat flow.In the process of directional solidification dendritic growth,the stray grains were easy to form in the variable cross-section region with the concave isotherm.The simulation results are consistent with the experimental results and the research results of related literatures,indicating that the improved cellular automaton method is effective and practical.