PVD法制备6.5%Si高硅钢薄板过程Si、Al共渗交互作用机制研究

The Fe-6.5 wt.% Si alloy has been regarded as an ideal core material due to its higher permeability, higher saturation magnetization and lower core losses than conventional Fe-3wt.% Si steel sheets especially at high frequencies. However, the high-Si alloys are known to be quite brittle, which brings about difficulty in conventional hot-cold rolling processes. This drawback restricts the application of Fe-6.5 wt.% Si alloy in practice. In the present work, physical vapor deposition (PVD) technique will be applied to deposit SiAl films onto double surfaces of low-Si steel substrates, to investigate effect of the deposition and diffusion variables on Si and Al distribution in the substrates in an attempt to clarify the underlying interaction mechanisms of Si and Al co-penetration into low-Si sheets, and discuss the possibilities of Al atom enhancing Si penetration in the diffusion process from kinetic calculation and the micro-structure analysis such as voids contents and dislocation densities. Finally, by optimizing the parameters and conditions, fabricate Fe-6.5 wt.% Si alloy from a conventional Fe-3 wt.% Si sheet, meanwhile the relationship of Al concentration and the magnetic and mechnical properties of fabricated Fe-6.5 wt.% Si alloy should be investigated to conclude a suitable Al ratio. Based on the better understanding of the the critical technology in the enriching-Si mechanisms, the conclusion is expected to be able to guide the fabrication of Fe-6.5 wt.% Si thin sheets by PVD approach in an industrial scale.

6.5%Si高硅钢具有磁感高、铁损低等优异软磁性能，是制作低噪音、低铁损铁芯的理想材料。但因B2和DO3有序相析出导致合金硬而脆，难于采用传统轧制工艺制成薄板。项目申请人发明了PVD法在低硅钢薄板双面共沉积富Si层并扩散制备6.5%Si高硅钢薄板的方法。前期研究发现Si渗速低是该技术实用化的技术瓶颈。本项目设计在低硅钢薄板双面PVD法沉积SiAl膜并进行高温真空扩散处理，通过研究膜层成分结构与扩散工艺参数等因素变化对Si、Al渗入低硅钢基体扩散行为的影响规律，弄清低硅钢基体Si、Al共渗交互作用机制和扩散动力学关系，从Al激发基体晶格缺陷如空位浓度、位错密度而降低Si扩散势垒的角度探讨Al助渗Si的可能条件及微观机理。最后通过工艺有效调控制成6.5%Si高硅钢薄板，并研究Al掺量变化与其组织结构及性能的内在联系，确定Al最佳掺比，为PVD法制备6.5%Si高硅钢薄板奠定理论和实践研究基础。

Fe-6.5%Si高硅钢因其高磁感应强度、低铁损和近零磁致伸缩系数等优势备受人们青睐，但其室温脆性问题一直是制约其工业化生产与应用的关键技术瓶颈。本项目采用磁控溅射镀膜技术在低硅钢薄板表面沉积富Si（Al）膜并经高温真空扩散处理，使膜层中Si（Al）原子在化学活度梯度的驱动作用下，渗入低硅钢基体，提高其Si（Al）浓度达到6.5%。项目基于Fe-Si-Al三元相图和DICTRA模拟软件开展了低硅钢基体Si、Al共渗制备Fe-6.5%Si-1%Al高硅钢合金最佳化的膜系结构设计和不同扩散工艺参数下Si与Al的浓度分布规律的模拟研究；在此基础上开展了不同镀膜工艺方式制备富Si(Al)膜的对比研究，确定出磁控溅射技术多靶共焦溅射沉积富Si(Al)膜较为适宜的工艺参数；然后开展了纯铁基体Si、Al共渗研究、低硅钢基体渗Al研究、低硅钢基体Si、Al共渗研究、低硅钢基体分步渗Al、渗Si研究，掌握了膜层组织结构以及扩散工艺参数变化对Si、Al渗入效果及其浓度分布的影响规律，发现浓度呈梯度分布的Si或Al元素促使另一方发生上坡扩散的内在机制来源于两种元素之间的排斥作用；在沉积的富Si(Al)膜中Al的存在可提高Si的化学活度，有助于加速Si的扩散；而在低硅钢基体中先渗Al再渗Si，Al对Si的扩散具有较强的阻缓作用。项目最后对比研究了制成Fe-6.5%Si和Fe-6.5%Si(Al) 高硅钢的软磁性能和力学性能，随低硅钢基体渗入Si与Al的浓度增加，合金的高频铁损值明显降低，Fe-6.5%Si高硅钢P1/10k值为25.5 W/kg，相比于初始低硅钢基板，降幅达到41%，Fe-6.5%Si-0.3Al高硅钢P1/10k值为26.82 W/kg，相比于初始低硅钢基板，降幅达到38%；制成的Fe-6.5(Si+Al)薄板可齐整剪切、可弯折成90度直角，塑韧性明显优于Fe-6.5%Si高硅钢合金。