电磁悬浮条件下液体钛合金的深过冷与热物理性质研究

Thermophysical properties of undercooled liquid alloys are very important for space application and rapid solidification science. However, it is usually difficult to achieve high undercooling by using conventional experimental method, and the specific heat and surface tension of undercooled liquid alloys cannot be determined. High undercooling and thermophysical properties of liquid Ti-based alloys are investigated by electromagnetic levitation containerless technique combined with molecular dynamics method in this project. Through electromagnetic levitation technique, the high undercooling state of liquid Ti-based alloys is obtained. Meanwhile, the surface tension and specific heat parameters of liquid Ti-based alloys are measured by oscillation drop method and drop calorimeter method, respectively. Crystal growth velocity versus the undercooling under electromagnetic levitation is also studied. Furthermore, distribution of temperature field and concentration field is calculated to show the rapid heat and mass transfer inside the alloy melt. The correlation mechanism between liquid structure, thermophysical properties and microstructure of Ti-based alloys is explored in this project.

深过冷液体高温合金的热物理性质对于空间应用科学和快速凝固科学至关重要。但是，常规实验方法不能实现高温合金熔体的深过冷，也就无法测定其比热和表面张力等热物性参数。本项目采用电磁悬浮无容器处理技术并结合分子动力学方法，系统研究液体钛合金的深过冷与热物理性质。通过电磁悬浮无容器处理技术，实现液体钛基合金的深过冷甚至超过冷状态。同时，采用悬浮液滴振荡法与落滴式量热计法，分别测定深过冷液体钛基合金的表面张力和比热等热物性参数。实验研究电磁悬浮条件下液体钛基合金晶体生长速度随过冷度的变化规律。系统计算深过冷钛基合金熔体内部的温度场与浓度场分布，进而揭示合金熔体内部的快速传热传质规律。阐明钛基合金的液态结构、热物理性质及微观组织之间的相关机制。

钛合金在航天航空领域被广泛地应用。本项目采用电磁悬浮无容器处理技术消除合金熔体异质晶核，实现钛基合金的深过冷甚至超过冷。实验与理论计算紧密结合，实验测定深过冷液态钛基合金的比热、表面张力等关键热物性参数，发现热物性参数与温度的依赖关系，系统阐释过冷度对热物性的影响规律；探索液态微观机构及热物性与过冷度之间的依赖关系。测定晶体生长速度随过冷度之间的变化关系，研究深过冷状态下液滴内部传热传质规律和非平衡快速凝固机制；测定钛基合金深过冷快速凝固样品的热扩散系数、热导率、热膨胀系数、比热等基础热物性参数，阐释超常凝固条件对大体积三维钛基合金制备的作用机制。