中文摘要：

针对Ti-6Al-4V合金熔模铸造固态相变过程中的微观组织演变，对a相片层的生长，采用了多组元Zener-Hillert模型计算片层边缘生长速率，根据溶质守恒，建立片层宽面的生长速率多元溶质扩散生长模型，模拟得到了多个口相集束竞争生长的微观组织。模拟结果表明，Ti-6Al-4V合金熔模铸造固态相变过程中，瑾相片层边缘生长受杂质元素影响较小，而在宽面上，杂质元素含量引起的过冷度占总过冷度的比例约为0．45；Ti-6Al-4V合金熔模铸造固态相变潜热约为70kJ／kg，与JMatPro软件中的数据吻合较好。模拟得到的组织形态结果与金相组织吻合较好，模拟得到的生长速率与实验估测的速率相当。

英文摘要：

Investment casting is widely used in producting complex thin-wall titanium alloy compo- nents. In this process, the β→α phase transformation decides the final microstructures of these compo- nents. However most of present studies on phase transformation of titanium alloys focus on the micro- structure evolution in heat treatment process or after deformation rather than in casting process now. It is a main reason only this work aims at the solid phase transformation of Ti-6Al-4V alloy in investment cast-ing. In this work, the growth model of edge of a phase plates based on multi component Zener-Hiller mod- el, and the growth model of broad face of a phase plates based on diffusion and conservation of multi components were established. The growth competition of different colonies, which consist of a phase plates in same orientation, was simulated and the microstructures and their evolution with temperature were obtained. The comparison between simulated microstructures and their evolution with temperature and experimental data indicated that the proportion of undercooling degree caused by impurities in the al- loy is about 45% of the total undercooling degree in broad face of a phase plates and a much smaller por- tion in edge of α phase plates. The comparison also showed that the enthalpy change of solid phase transformation of titanium alloy is about 70 kJ/kg. The simulated and experimental morphologies look like similar and the simulated growth rate is also in good accordance with experiment inferred qrowth rate.