稳恒磁场对Fe-Si复合电镀层形貌及Si含量的影响

EFFECT OF STATIC MAGNETIC FIELD ON THE MORPHOLOGY AND Si CONTENT OF Fe-Si COMPOSITE COATING

将平均粒径为2μm的Si粉分散于镀铁液中,对水平稳恒磁场下复合电沉积法制备Fe-Si复合镀层过程进行了研究,探讨了磁感应强度及位向、电流密度等对Fe-Si复合镀层形貌及Si含量的影响规律.结果表明,采用竖直电极电镀时,在0—1 T磁感应强度下,无论施加平行磁场还是垂直磁场,镀层Si含量均随着磁场强度的增加而增加,特别对平行磁场而言,镀层Si含量从无磁场的1.23%(质量分数,下同)增加到1 T时的39.80%;采用水平电极电镀时,由于重力沉降效应,阴极镀层Si含量可高达37.94%,然而施加垂直磁场后,复合镀层Si含量随磁感应强度增加而急剧下降,1 T时仅为2.83%,并且阴极镀层表面出现与磁场方向垂直的条状铁基质突出物,同时微米Si颗粒沿着突出物延伸方向分布.在1 T磁场下,无论是水平电极还是竖直电极,施加垂直磁场电镀获得的镀层Si含量均随着电流密度的增大而减小,但竖直电极平行磁场电镀获得的镀层Si含量随着电流密度的增加而先增大后减小,在20 mA/cm2时镀层颗粒含量达到最大值.理论分析表明,施加不同位向的稳恒磁场后,电解液中形成的宏观磁流体动力学(MHD)效应和微区MHD效应,是影响复合镀层形貌和Si含量的关键原因.

The Si particles with average size of 2 μm were dispersed in plating solution, and the electrodeposition process of Fe-Si composite coating under a static magnetic field was studied. The influences of orientation, flux density of magnetic field （MFD） and current density on the morphol- ogy and Si content of Fe Si composite coatings were discussed. It was found that the Si content of coatings for vertical electrodes increased significantly with increasing the MFD in both parallel and perpendicular magnetic field （regard to current） with the MFD ranging from 0 T to 1 T. In the case of aclinic electrodes, the Si content of coating can reach 37.94% （mass fraction） without magnetic field. However, after applying a perpendicular magnetic field, the Si content of coatings decreased sharply with increasing the MFD （only 2.83% at 1 T）. Meanwhile, many striated iron matrix protuberances with Si particles appeared perpendicular to the direction of magnetic field on the coatings surface. Moreover, the Si content of coatings decreased with increasing current density for both aclinic and vertical electrodes in 1 T perpendicular magnetic field, while that for vertical electrodes first increased and then decreased and reached maximum value at about 20 mA/cm2 in 1 T parallel magnetic field. Theoretical analysis shows that the change of morphology and Si content of coatings were mainly at- tributed to the formations of macroscopic magnetohydrodynamics （MHD） and micro-zone MHD effect caused by Lorenz force.