电磁悬浮条件下液态Fe_(50)Cu_(50)合金的对流和凝固规律研究  

Fluid convection and solidification mechanisms of liquid Fe_(50)Cu_(50)alloy under electromagnetic levitation condition

作　　者：林茂杰[1] 常健[1] 吴宇昊[1] 徐山森[1] 魏炳波[1] 

机构地区：[1]西北工业大学应用物理系,西安710072

出　　处：《物理学报》2017年第13期191-199,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51401167;51327901);中央高校基本科研业务费专项资金(批准号:3102015ZY097)资助的课题~~

摘　　要：基于轴对称电磁悬浮模型,理论计算了二元Fe_(50)Cu_(50)合金熔体内部的磁感应强度和感应电流,分析了其时均洛伦兹力分布特征,进一步耦合Navier-Stokes方程组计算求解了合金熔体内部流场分布规律.计算结果表明,电磁悬浮状态下合金内部流场呈现环形管状分布,并且电流强度、电流频率或合金过冷度的增加,均会导致熔体内部流动速率峰值减小,平均流动速率增大,并使流动速率大于100 mm·s^(-1)区域显著增大.通过与静态凝固实验对比发现,电磁悬浮条件下熔体中强制对流使得合金内部富Fe和富Cu区的相界面呈波浪状起伏形貌,并且富Cu相颗粒在熔体上部分出现的概率增加.In the electromagnetic levitation experiment, the liquid flow in the undercooled liquid alloy remarkably affects the relevant thermodynamic property measurement and solidification microstructure. Therefore, it is of great importance to understand the fluid convection inside the undercooled melt. Theoretical calculation and electromagnetic levitation experiment have been used to investigate the internal velocity distribution and rapid solidification mechanism of Fe50Cu50 alloy. Based on axisymmetric electromagnetic levitation model, the distribution patterns of magnetic flux density and inducted current for levitated Fe50Cu50 alloy are calculated together with the mean Lorenz force. The Navier-Stokes equations are further taken into account in order to clarify the internal fluid flow. The results of the theoretical calculation reveal that the fluid velocity within levitated melt is strongly dependent on three factors, i.e., current density, current frequency and melt undercooling. As one of these factors increases, the maximum fluid velocity decreases while the average fluid velocity increases. Meanwhile, the area with fluid velocity larger than 100 mm·s-1is significantly extended.Furthermore, the fluid flow within levitated melt displays an annular tubular distribution characteristic. The Fe50Cu50 alloy melt is undercooled and solidified under electromagnetic levitation condition. In this undercooling regime ？T 69 K, solidification microstructures are composed of dendrites, and a morphology transition of ＂coarse dendrites →refined dendrites＂ is observed with the increase of melt undercooling. Comparing with the critical undercooling of metastable liquid phase separation in the glass fluxing experiment, the forced flow within the Fe50Cu50 alloy melt has suppressed phase separation substantially. Once the undercooling attains a value of 150 K, metastable phase separation leads to the formation of layered pattern structure consisting of floating Fe-rich zone and sinking Cu-rich zone. A core-shell macrosegre

关 键 词：电磁悬浮 对流 深过冷 相分离 

分 类 号：TG111.4[金属学及工艺—物理冶金]