电磁搅拌铝合金熔体速度场计算及分析

为优化电磁搅拌工艺,用ANSYS软件对圆柱形铝合金熔体速度场进行了数值模拟.结果表明:在小于0.86倍熔体半径的范围内,熔体切向运动为强迫涡.涡核旋转角速度约为电磁场同步转速的1/26.涡核与坩埚壁间的熔体径向流层间具有较大的剪切速率,这对增强颗粒的润湿复合以及半固态组织的获得有利；而在涡核内,剪切速率接近于0,因此没有这种作用.采用环状熔体是解决该问题的办法之一.熔体纵切面内剪切速率的计算结果表明,剪切速率随半径增大而增大,而在高度方向上,则呈现中间大、上下两端小的特点.运动轨迹的计算说明,总体上,熔体质点呈螺旋式上升,但底部熔体流速低,且其运动范围基本上限于底部,易导致增强颗粒沉淀于底部,不利于其均匀分布.

Calculation and Analysis of Aluminum Alloy Melt Velocity Field Under Electromagnetic Stirring

To optimize electromagnetic stirring process,the velocity field simulation of cylindrical aluminum melt was done by using ANSYS software.The results show that within the range of 0.86 times melt radius,the tangential movement of melt was forced vortex.The rotational angular velocity of vortex core was 1/26 of the electromagnetic field synchronization rotational velocity.The radial flow layer between vortex core and crucible wall had great shear rate.The great shear rate did favor to wettability and composite of reinforced particle and getting semi-solid microstructure.In contrast,the shear rate was close to zero in vortex core,so there was no good wettability and composite function in this area.Adopting ring melt was an approach to solving the problem.Calculation of melt longitudinal section shear rate showed that the shear rate increased with increase of radius.In the altitude direction,distribution of the shear rate was small at two ends and big in the middle.Overall,the trace calculation showed melt particulates rose corkscrewly.But at bottom,the melt velocity was low,the melt particulates motion range was basically at the bottom,which made reinforced particles precipitate at bottom,and did harm to uniform distribution of the particles.