镍基单晶高温合金定向凝固组织的数学模型表征

Characterization of As-cast Microstructure of Ni-based Superalloys Based on Mathematical Models

通过改变定向凝固工艺研究了镍基单晶高温合金铸态组织的演化规律,并用数学模型对试验结果进行了拟合。结果表明,随着抽拉速率的增大,合金铸态组织的凝固界面经历了胞状-粗枝状-细枝状的转变;铸态组织一次枝晶间距试验结果介于Hunt模型和Trivedi模型之间;通过对试验数据的非线性回归分析,得到一次枝晶间距λ1和抽拉速率V之间满足的回归公式;随抽拉速率的增大,二次枝晶间距减小,但Re和Ru的添加对一次和二次枝晶间距的影响较小。

With the varied solidification parameters, the evolutions of as-cast microstructure ofNi-based superalloys were investigated. In addition, the as-cast microstructure was characterized by mathematical models. The results show that as-cast microstructure gradually change from cellular structure to coarse dendrite, and then to fine dendrite, with the increasing withdrawal rates; Compared with the theoretical models of primary dendrite arm spacing, the results of nonlinear regression analysis shows the primary dendrite arm spacing between Trivedi＇s and Hunt＇s models. The relationship between primary dendrite arm spacing and withdrawal rate is proposed. Moreover, the secondary dendrite arm spacing decreased with the increasing withdrawal rate. However, the influence of Re and Ru additions on the primary and secondary dendrite arm spacing can be neglected.