高温合金定向凝固过程中通道偏析的物理模拟研究

摘要

利用NH4Cl-H2O溶液凝固实验,对高温合金定向凝固中的通道偏析进行物理模拟,研究通道偏析的形成过程以及溶液中 NH4Cl 的质量分数 w(NH4Cl)和初始基板温度对通道偏析数目和形貌的影响.结果表明,除了w(NH4Cl)为15%外,w(NH4Cl)为24%、27%和30%的NH4Cl?H2O溶液凝固时均形成通道偏析.随凝固时间延长,通道偏析数目先逐步增加然后减少,形貌辨识程度增加.随w(NH4Cl)增加,通道偏析数目减少,形貌辨识程度增加.随初始基板温度下降,通道偏析数目减少,形貌辨识程度增加.影响通道偏析的主要因素可归结为影响偏析形成和通道形成的因素,包括合金成分、温度梯度和凝固速率.%NH4Cl-H2O solution systems were used to simulate the formation process of the channel segregation during the directional solidification of superalloys. The formation of the channel segregation was investagted. The effects of the NH4Cl concentrations and the initial base temperature on the channel segregation were also studied. The results show that the channel segregation forms in the solution systems of the concentrations of 24%, 27% and 30% except for 15%. The number of channel segregation increases first and then decreases, and the morphology becomes more pronounced with the increasing time during solidification. The quantity of channel segregation decreases and the morphology becomes more pronounced with the increasing concentration. The change of the quantity and morphology of the channel segregation with the decreasing of the initial base temperature shows the same trend as that with the increasing of concentration. The main factors controlling the channel segregation can be attributed to the formation of the channel and the segregation, which include alloy composition, solidification rate and temperature gradient.