混沌对流下的半固态A356铝合金初生相形貌演变研究  

RESEARCH ON MORPHOLOGY EVOLUTION OF PRIMARY PHASE IN SEMISOLID A356 ALLOY UNDER CHAOTIC ADVECTION

作　　者：刘政[1] 张嘉艺[2] 罗浩林[2] 邓可月 

机构地区：[1]江西理工大学机电工程学院,赣州341000 [2]江西理工大学材料科学与工程学院,赣州341000

出　　处：《金属学报》2016年第2期177-183,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51144009和51361012;江西省自然科学基金项目20142bab206012;江西省教育厅科技项目GJJ14407资助~~

摘　　要：研究了半固态A356铝合金熔体中混沌对流的表征,及电磁场诱发的混沌对流对半固态A356铝合金熔体中初生相形貌演变的影响.通过Fluent软件研究了电磁场作用下A356铝合金熔液中微粒的流动轨迹,计算了这些流动轨迹的Kolmogorov熵和分形维数,证明了施加适当的电流频率能在合金熔体中产生混沌运动.结合实验研究,对不同电流频率及工艺参数的实验结果进行对比.研究结果表明,A356铝合金熔体在650℃浇注,电流频率为30 Hz的电磁场中搅拌15 s,并在590℃保温10 min,此时凝固系统的Kolmogorov熵为6829.5 nat/s,分形维数为2.2439,初生相的平均等积圆直径为59.86 mm,平均形状因子为0.71,此时晶粒最圆整细小,组织形貌最佳.Chaotic advection could be strengthened mix, mass transfer and heat transfer in the viscous fluid, the melt flow forming was affected by electromagnetic field in the metal solidification process, so were the macro and microstructure of materials. So it was necessary to study chaotic characteristics of semisolid Al alloy in the electromagnetic field. The characterization of chaotic convention and morphology of primary phase were mainly researched in semisolid A356 alloy under the electromagnetic field. The trajectories of the particle in semisolid A356 alloy melt was simulated by the computational fluid dynamics software Fluent, the Kolmogorov entropy and fractal dimension of the flow trajectories of semisolid A356 alloy melt were judged and analyzed. The results showed that chaotic advection may happen in semisolid alloy melt under electromagnetic field. Combined with experiment, the results of process parameters and different current frequencies were compared. The results showed that the primary phase with 59.86 μm in average equal-area circle diameter, 0.71 in average shape factor, 6829.5 nat/s of Kolmogorov entropy and 2.2439 of fractat dimension can be obtained in semisolid A356 alloy with pouring 650℃, stirring for 15 s at 30 Hz, and holding at 590℃ for 10 min. Meanwhile, the morphology of primary phase can be observed with the best parameters.

关 键 词：半固态A356铝合金 混沌对流 Kolmogorov熵 分形维数 电磁搅拌 

分 类 号：TG292[金属学及工艺—铸造] TP391.9[自动化与计算机技术—计算机应用技术]