( 1. 哈尔滨工业大学 材料科学与工程学院， 哈尔滨 150001;
2. 西北工业大学 材料科学与工程学院， 西安 710072)
摘 要: 考察了包晶合金分别在定向凝固初始过渡及稳态生长阶段的凝固特性; 分析了凝固过程中液-固界面前沿两相形核过冷与成分过冷的条件及温度梯度(G)和生长速度(v)对两相竞争生长的影响和带状结构形成与共生生长的条件, 确定了出现带状结构所必需的成分和G/v条件。 计算了TiAl合金在初始过渡阶段初生相及包晶相的竞争生长和向稳态发展的过渡机制, 并应用界面响应函数建立了不同成分TiAl合金在稳态生长过程中相与组织随生长速度演化的竞争选择模型及相应的凝固组织图, 预测了TiAl合金在不同凝固条件下可能形成的相与组织形态。在所选的合金成分范围内定向实验所得的凝固组织与计算预测的组织选择图有较好的一致性。
关键字: TiAl包晶合金; 定向凝固; 组织选择
（ 1. School of Materials Science and Engineering,
Harbin Institute of Technology, Harbin 150001, China;
2. School of Materials Science and Engineering,
Northwestern Polytechnical University, Xian 710072, China）
Abstract: The examination on solidification characteristics of Ti-Al peritectic alloys was dealt with in both initial transient and steady state separately, the nucleation and constitutional supercooling of both phases at the solid/liquid interface and the effect of thermal gradient and growth velocity on the competitive growth of two phases were analyzed, and the condition of band structure formation and coupled growth was also determined. The composition range and G/v ratio to form the band structures were determined. The competitive growth between primary and peritectic phases was investigated during the initial transient and their development to steady-state growth for TiAl alloy, and the interface response functions were used to determine the selection map of phases and microstructures at different compositions and growth rates during the steady-state growth. The microstructures from directionally solidified TiAl alloys with given compositions were in good agreement with the predicted selection map.
Key words: TiAl peritectic alloy; directional solidification; microstructure selection
