Fe基非晶软磁合金性能与微结构的关联性研究

Fe-based amorphous soft magnetic alloys have been paid much attention because of their excellent magnetic properties and simple preparation processes. However, the correlations between the glass-forming ability, the thermostability and magnetic properties and the microstructure is not clear enough, which greatly restricted the development and application of Fe-based amorphous soft magnetic alloys especially those with excellent performances and large size. Aiming at the key scientific problem of the correlation between the properties and the microstructure in Fe-based amorphous soft magnetic alloys, in this project we try: (1) In-depth understanding the internal relations between the glass-forming ability, the thermostability and magnetic properties and the microstructure of Fe-based amorphous soft magnetic alloys; (2) Seeking the profitable clusters and their connections which can promote both magnetic properties and the glass-forming ability of Fe-based amorphous soft magnetic alloys; (3) Investigating the mechanism of the magnetic interaction among clusters and its effect on magnetic properties of Fe-based amorphous soft magnetic alloys; and (4) Revealing the mechanism of the evolution of the type and scale of clusters and its effect on the thermostability and magnetic properties in the process of structural relaxation of Fe-based amorphous soft magnetic alloys and that before the crystallization of Fe-based nanocrystalline soft magnetic alloys. This project has great significance in both enriching the research connotation of the correlation between properties and the microstructure of amorphous alloys and promoting the application of Fe-based amorphous soft magnetic alloys with excellent performances and large size.

Fe基非晶软磁合金因优异的磁性能和简单的制备工艺而受到广泛关注。但其非晶形成能力、热稳定性及磁性能与微结构的关联性目前尚不够明确，这极大地制约了该类合金特别是高性能、大尺寸Fe基非晶软磁合金的开发与应用。本项目针对Fe基非晶软磁合金中性能与微结构关联性这一关键科学问题：（1）深入认识Fe基非晶软磁合金非晶形成能力、热稳定性及磁性能与微结构的内在联系；（2）寻求对Fe基非晶软磁合金的磁性能和非晶形成能力均有促进作用的“有益”团簇和“有益”连接方式；（3）探讨团簇间磁性相互作用及其对Fe基非晶软磁合金磁性能的影响机制；（4）揭示Fe基非晶软磁合金结构弛豫过程中以及Fe基纳米晶软磁合金晶化之前团簇类型与尺度等的演变规律及其对合金热稳定性与磁性能的影响机制。本项目对于丰富非晶合金性能与微结构关联性的研究内涵、推动高性能大尺寸Fe基非晶软磁合金的应用具有重要意义。

具有优异软磁性能且制备工艺较为简单的Fe基非晶合金受到广泛关注。但是，对Fe基非晶软磁合金的微结构与性能（尤其是应用最为广泛的软磁性能）之间关联性的研究还不够深入，Fe基非晶合金在结构弛豫过程中短/中程有序结构（团簇及其连接）的演变对其性能的影响机制还不够明确，晶化前的微结构演变对合金的热稳定性、后续晶化行为及其纳米晶产物的结构及磁性能是否有影响以及如何影响仍有待进一步研究。.在本项目研究中，一方面，我们通过高能同步辐射技术辅以计算机模拟获得Fe基非晶合金的短程及中程有序结构信息，结合穆斯堡尔谱技术和磁测量获得的磁性能信息，揭示合金微结构对宏观性能的影响规律并寻求对合金的磁性能和非晶形成能力均有提升作用的“有益”团簇及其连接。我们发现结构弛豫过程中，Fe基非晶合金中的类二十面体团簇含量增加，团簇畸变程度降低，同时随着原子层从里到外，合金中拉应力区域与压应力区域相间分布并且体积热应变值逐渐减小，从而逐渐释放内应力。同时，结构弛豫诱导易磁化轴向带材面内转动。内应力的释放以及易磁化轴的转动共同导致合金的磁软化。在FePC非晶合金中，理想二十面体团簇含量较高的合金成分非晶形成能力较好，然而其饱和磁感应强度却较低。此外，我们在FeCoSiBNb非晶合金中发现一种由团簇间连接决定的不同于结构弛豫的结构重排，其会重新引入内应力并增强磁弹性各向异性从而导致合金的磁硬化。.另一方面，研究发现Fe基非晶软磁合金结构弛豫过程中所发生的微结构演变能够显著影响纳米晶产物的结构和磁性能。含有Cu元素的Fe基非晶合金体系在晶化之前，Cu元素不断从基体中析出，形成“有益”的Cu团簇为α-Fe纳米晶提供异质形核位置，有助于细化最终纳米晶产物的晶粒并提高结晶度。基于这一认识，我们设计并引入几种退火工艺，如两步退火、分步退火、循环退火等，成功提高了纳米晶产物的综合软磁性能。.本项目对于丰富非晶合金性能与微结构关联性的研究内涵、推动高性能Fe基非晶/纳米晶软磁合金的应用具有重要意义。