间歇式永磁搅拌对高纯铝凝固组织的影响

Effect of intermittent permanent magnet stirring on solidification structure of high purity aluminum

为研究间歇式永磁搅拌对高纯铝凝固组织的影响,采用永磁搅拌机对铝熔体进行14种不同方式的间歇式搅拌,观察不同的间歇式搅拌对其凝固组织的影响。结果表明:以300r/min的速度搅拌,高纯铝凝固组织的等轴晶区较大,等轴晶尺寸更小,但是会在铸锭的芯部形成气孔等缺陷;当正反方向间歇式搅拌和正正方向间歇式搅拌分别为转3T停1s和转2T停1s时,高纯铝的凝固组织的等轴晶最多且缺陷最少,其中正反间歇式搅拌效果更好;等轴晶由柱状枝晶的二次枝晶臂脱落而形成,是由强迫对流引起的;搅拌速度越大,熔体流动速度越大,从而增加二次枝晶臂脱落的概率。

In order to study the effect of intermittent permanent magnet stirring on solidification macrostructure of high purity aluminum,the permanent magnet mixer was used to carry out 14 different stirring methods and the overall solidification structure was analyzed through the observation of its macrostructure.The results show that at 300 r/min,the equiaxed crystal area of the high-purity aluminum solidification structure is larger while the equiaxed crystal size is smaller.However,defects such as pores can be formed in the core.The equiaxed grains are the most and the defects are the fewest when the positive-negative intermittent stirring rotates 3 turns and stops for 1 s,and the positive-positive intermittent stirring rotates 2 turns and stops for 1 s.The effect of positive and negative intermittent stirring is better.At the same time,the equiaxed grain is formed by the secondary dendrite arm detachment of columnar dendrites,which is caused by forced convection.The greater the rotation speed is,the higher the flow velocity is,which increases the probability of the secondary arm detachment.