( 1. 国防科技大学 航天与材料工程学院 新型陶瓷纤维及其复合材料国防科技重点实验室，长沙 410073；
2. 西北工业大学 凝固技术国家重点实验室， 西安 710072)
摘 要: 从非稳态传热角度并按照柱坐标系中二维传热方式对Bridgman装置中Al柱状试样近快速定向凝固过程进行了数值模拟，分析了试样在近快速定向凝固过程中液固界面前沿的温度梯度和生长速度随试样抽拉速度的变化规律。 计算结果表明： 在30～3000μm/s的抽拉速度范围，随着抽拉速度的提高， 液固界面前沿的温度梯度在（145±10）K/cm范围变化， 生长速度与抽拉速度的差别不超过5%。 研究结果为实验研究近快速定向凝固组织形态转变提供了可靠的控制参数依据。
关键字: 近快速定向凝固； Al柱试样；数值模拟； 温度梯度； 凝固速度
Al bar sample
（ 1. Key Laboratory of National Defense Technology for Advanced Ceramic Fibers and Composites,
College of Aerospace and Materials Engineering,
National University of Defense Technology,
Changsha 410073, China;
2. State Key Laboratory of Solidification Processing,
Northwestern Polytechnical University, Xi′an 710072, China）
Abstract: An universal method of numerical simulation on near-rapid directional solidification of Al round bar in a vertical Bridgman furnace was developed, in which the transient heat transfer equations were used and the longitudinal heat conduction is taken into account. The influence of pulling velocity on the temperature gradient and growth velocity of liquid-solid interface was analyzed. The results indicate that, in the pulling velocity range of 30～3000μm/s, the change of pulling velocity on the temperature gradient and growth velocity of liquid-solid interface is hardly obvious. With pulling velocity increasing, the temperature gradient is changed from 135 to 155K/cm, and the difference of growth velocity and pulling velocity is within the range of 5%. The numerical simulation of the near-rapid directional solidification of Al sample can provide an available tool for the investigation on the selection of microstructure of binary sing-phase Al-Zn alloy under near-rapid directional solidification condition.
Key words: near-rapid directional solidification; Al round bar sample; numerical simulation; temperature gradient; growth velocity
