纵向强静磁场对定向凝固DZ417G合金枝晶形态和数目的影响

INFLUENCE OF A LONGITUDINAL STRONG STATIC MAGNETIC FIELD ON THE DENDRITE MORPHOLOGY AND QUANTITIES FOR DIRECTIONALLY SOLIDIFIED DZ417G SUPERALLOY

纵向强静磁场可明显影响高温合金DZ417G的定向凝固组织,为控制定向组织树枝晶数目提供了一种新手段。在抽拉速率为5μm/s时,强磁场影响了该合金组织的定向凝固生长特性,影响程度随磁场强度的加大而增加。当抽拉速率达到40μm/s及其以上时,施加强磁场使得单位面积上的枝晶数目增加,枝晶数目随磁场强度的增大而增大,增大幅度最大达到一倍左右。当温度梯度增大时,强磁场在低抽拉速率(5μm/s)下影响该合金定向凝固的效应加剧,在抽拉速率40μm/s及其以上时增加枝晶数目的效应也加大。从磁抑制对流和热电磁效应方面分析了上述现象,提出了作用机理。

The investigated results showed that a longitudinal strong static magnetic field could dramatically affect the microstructure of directionally solidified DZ417G superalloy, indicating a new way of controlling the dendrite quantities. The morphology of directional dendrite growth for the superalloy was influenced by strong static magnetic field at the withdrawal velocities of 5μm/s. The disturbed extent was increased with the increasing of magnetic field intensity. When the withdrawal velocity reached to 40μm/s or above, the strong magnetic field increased the dendrite number per area by one time. The temperature gradient enlarged the effects of strong magnetic field on the microstructure of directionally solidified DZ417G superalloy. The above phenomena were analyzed on the base of the theories of magnetic convection damping and thermo-electromagnetic convection in detail.