混沌对流中不同稀土元素对半固态铝合金初生相形貌研究

Research on Morphology Evolution of Different Rare-earth Elements on Primary Phase in Semisolid Aluminum Alloy under Chaotic Advection

研究不同半固态稀土铝合金熔体混沌对流的表征及在不同电磁搅拌频率和时间下诱发的混沌对流对加入相同量La及Yb的半固态A356铝合金初生相形貌演化的影响。用Fluent流体力学软件模拟电磁场作用下A356铝熔液中微粒的流动轨迹,计算流动轨迹的混沌特征量Kolmogorov熵,发现只要适当施加电磁场,Kolmogorov熵值随电磁搅拌频率及时间的增大而增加。结合试验,添加两种等量不同稀土对A356铝合金初生相形貌影响,并施加不同搅拌频率及时间的试验参数后,两者都在搅拌频率30 Hz、搅拌时间15 s时,初生相形貌最理想,晶粒细小圆整且Kolmogorov熵值达到最大。但A356-Yb铝合金的初生相形貌优于A356-La铝合金初生相形貌。通过模拟和试验,混沌看似无规则但其中暗含着规律,加入的稀土和施加的磁场频率及时间都互相影响混沌对流下的合金初生相形貌。

The characterization of chaotic convention and morphology of primary phase are mainly researched in different semisolid rare-earth La and Yb of A356 alloy under the different time and frequencies of electromagnetic field. The trajectories of the particle in semisolid A356 alloy melt are simulated by the computational fluid dynamics software Fluent, and the results of Kolmogorov entropy are calculated. The results show that Kolmogorov entropy is higher accompanied by the increasing frequencies and time. Combined with experiments, the primary phase in A356 semisolid is effected by the two same contents rare-earth at different stirring frequencies and time. The morphologies of primary phase are both observed better than stirred for 15 s at 30 Hz, meanwhile, the morphology of A356-Yb primary phase is observed better than A356-La primary phase. Through the simulation and experiment, random chaos imply the rules, the morphology of primary phase is effected by added rare-earth, electromagnetic stirring frequencies and time.