考虑包晶反应的Ti-(45-48)Al合金锭凝固组织模拟

提出了一种新的模拟Ti-（45-48）Al（原子分数，％）合金锭凝固组织形成的随机性方法．将元胞分为先析出相元胞和包晶相元胞两类，不同的元胞凝固路径不同．借助于这种方法，在最终的模拟结果中可以显示包晶相的随机分布．计算中考虑了一次缩孔的形成，对于大尺寸铸锭的模拟，提出了特殊移动内存分配方法，以节约计算时间和计算量．对比模拟结果和实验结果验证了模型的可行性，分析了凝固参数对凝固组织的影响．模拟结果表明流动强度的增大以及合金元素成分的增加均有助于等轴晶区的形成．随着合金成分的增加，包晶相的数量增加．

SIMULATION OF MACROSTRUCTURE EVOLUTION IN Ti-(45~48)at%Al ALLOY INGOT

Solidified structure modeling of Ti-(45-48)A1 alloy (atomic fraction, %) ingot has been carried out by using a new cellular automaton method coupled with macroscopic heat transfer calculation. Cells are divided into primary and peritectic ones. Different cells take the different solidification paths. By the new method, the formation of peritectic phases can be shown graphically throughout solidification. The formation of shrinkage cavity at the top of the ingot is included in the calculation. A special-moving-allocation technique is designed to minimize the computation costs and memory size associated with a large number of cells. The potentiality of the present model is demonstrated by comparing the simulated results with the experimental one. The influences of convection and initial alloy composition on the grain structures are studied and the mechanisms producing these results are discussed. The simulated results indicate that the size of equiaxed zone increases with increasing the convection coefficient and alloy composition. And the number of peritectic phases decreases as the alloy composition decreases.