高(Si+Al)成分梯度与取向FeSi合金的复合化及其性能研究

Soft magnetic alloys are required to possess high magnetic induction, low losses as well as mechanical properties for the purpose of miniaturization and lightweight of electrical devices. Design and preparation of soft magnetic alloys with multi-functionality are of significance from scientific and technological perspective, to meet the needs of working characteristics of the devices. In this respect, this proposal is devoted to designing and preparing soft magnetic alloys exhibiting Goss texture with (Si+Al) gradient distributions across the alloy surface layers, which was inspired by high electrical resistivity and nearly zero magnetic anisotropy and magnetostrictive coefficient for FeSiAl alloys, and by the high magnetic induction and good mechanical properties for FeSi alloys with Goss texture. Up to date, penetration temperature of Si into a FeSi alloy with low Si content has to be as high as 1200?C, in order to obtain a smooth surface with no void in it. Surface gradient thickness along with gradient distribution is therefore hardly controllable, and the initial texture structure of the low-silicon steel substrate is also inclined to be destroyed. This proposal aims to apply a surface nano-processing onto grain oriented silicon steels to enhance low-temperature diffusion rate of atoms, which is of significance in realizing a feasible approach of (Si+Al) surface penetration at low temperatures necessary for the initial microstructure of the oriented silicon steel to be retained. The surface nanotechnology by mechanical treatment allows CVD production line available, which is believed to be generalized as a promising processing from the viewpoint of industrialization.

器件的小型化与轻量化发展需要软磁材料同时具有高磁感应强度、优异的交流特性和力学性能，根据软磁器件工作特点进行结构复合化设计制备软磁材料是一个重要发展趋势。本申请根据FeSiAl合金具有电阻率高、结晶磁各向异性和磁致伸缩系数同时趋近于零的特点，提出将其复合于具有高磁感应强度和良好力学性能的取向硅钢薄板表面，形成高（Si+Al）成分梯度层与取向组织并存的复合结构。另一方面，目前表面无孔洞高Si或高Al成分梯度的制备均需在1200?C高温下进行，导致表面梯度层厚及梯度分布难以控制且易破坏低硅钢取向结构，本项目提出采用表面机械研磨技术对低硅取向硅钢表面进行纳米化处理，提高原子的低温扩散速率，发展一种表面低温Si、Al共渗方法，在获得(Si+Al)梯度结构的同时保持基体取向硅钢的组织结构。所采用的表面机械研磨技术只是在传统的化学气相沉积过程中增加一道工序，因而可实现连续生产，具有工业化推广价值。

采用表面机械研磨法在Fe-3wt.%Si取向合金表面制备出了具有纳米结构的表面应变层。结合化学气相沉积法，在1000℃以下，制备出了具有优异高频软磁性能和力学性能的高Si、（Si+Al）成分梯度取向软磁合金。获得了表面纳米结构对元素扩散的影响规律并在此基础上建立了扩散方程，实现了对截面元素分布的控制。针对梯度合金在高频交变磁场下的磁化行为进行研究，发现梯度取向合金的高频铁损与成分梯度和磁畴结构密切相关。基于涡流损耗与趋肤效应的相互关系，获得了影响趋肤深度的关键因素，并且通过磁畴结构的观察揭示了反常损耗与其的内在关联。针对梯度合金的直流软磁性能进行研究，发现成分梯度会导致磁致伸缩系数的增加，进而合金矫顽力增大；然而由于成分梯度有利于磁晶各向异性场的降低，且涡流损耗也显著降低，使梯度合金的交流损耗明显下降，该结果在高频下尤其显著。课题还获得了 Si/Al含量比对梯度合金磁性能（饱和磁感应强度、磁导率、电阻率、交流损耗等）与力学性能的影响规律。