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建立凝固过程的数学模型来揭示自由晶核的迁移行为。模拟结果表明:在脉冲电流作用下,大多数形成于熔体上表面的晶核将往下迁移并随机分布于Al熔体内部,提供更多的形核质点,进而细化凝固组织晶粒。同时,研究在施加脉冲电流(ECP)时晶核尺寸对晶核分布和细化的影响。小尺寸的晶核同周围熔体一同运动,迁移距离较短;而大尺寸的晶核在脉冲电流作用下以较快的速度相对于周围熔体运动,有利于熔体内部晶粒的细化。该研究有利于加深对脉冲电流细化凝固组织机理的认识。
A mathematical model of the solidification process is established to reveal the migration behavior of free nuclei. The simulation results show that most of the nuclei formed on the upper surface of the melt will migrate downwards and randomly distribute inside the Al melt under the action of the pulse current to provide more nucleation sites and refine the solidified grains. At the same time, the effect of nucleation size on the distribution and refinement of nuclei during impulse current (ECP) was investigated. Small nuclei move along with the surrounding melt and have a short migration distance. Large nuclei move relatively fast with the surrounding melt under the action of pulse current, which is beneficial to the grain refinement in the melt . This study is beneficial to deepen the understanding of the mechanism of pulsed current refinement and solidification.