在脉冲电流或脉冲磁场作用下LY12合金的凝固组织

在LY12铝合金凝固过程中施加脉冲电流或脉冲磁场，研究脉冲电流或脉冲磁场对这种合金凝固组织的影响。结果表明，脉冲电流和脉冲磁场均可使晶粒明显细化，等轴化，在脉冲电磁艇下金属凝固组织的晶粒细化机制为：在脉冲电磁场的作用下剧烈的强迫对流促进晶粒从型壁上游离，大大增加金属熔体的形核率，导致晶粒细化；温度相对均匀使得游得的晶粒得以保存下来，抑制了晶粒在某个方向上的优先,从而抑制了树枝晶的形成。

SOLIDIFICATION STRUCTURES OF LY12 AL-ALLOY UNDER PULSED CURRENT AND PULESD MAGNETIC FIELD

The effect of pulsed current and pulsed magnetic field on the solidification structures of LY12 aluminum alloy was studied. It was found that both pulsed current and pulsed magnetic field can notably improve the solidification structures, make the grain obviously refine and equiaxed. The theoretical analysis of the refinement mechanism of these two ways showed that the severe force convection under electromagnetic field promote the grain dissociate from the mold wall, thus the nucleation rate was greatly increased, thereby the grain was refined. The dissociative grains were saved and the priority growth at one direction was restrained because of the relative uniform temperature field, consequently the nondendritic structure was formed.