各向异性块体Sm2Co17/FeCo异质纳米永磁材料的制备和结构控制

针对Sm2Co17/FeCo异质纳米永磁材料发展面临的关键科学问题，本项目拟采用组合极端变形和亚稳相转变相结合的策略来控制其软、硬磁纳米晶结构。通过机械合金化在Sm-Co非晶基体中引入极小尺寸（< 10 nm）、分布均匀的高分数（> 20%）FeCo相，以控制软磁相结构。采用高压热压缩（HPTC）变形来截获SmCo亚稳相。研究极端变形下非晶前驱物中SmCo亚稳相的形成、取向生长和纳米晶化，研究取向SmCo亚稳相在低温（或短时）退火中向Sm2Co17的转变和织构遗传，获得Sm2Co17纳米晶织构。研究组合极端变形和SmCo亚稳相转变对FeCo相结构和Sm2Co17晶体取向的调控；揭示HPTC变形下SmCo亚稳相择优生长和退火过程中Sm2Co17纳米晶织构形成的机制。研究异质纳米材料的界面结构和磁性。建立“工艺/成分－微结构－磁性”的关系，发展高性能异质纳米永磁材料制备的新原理和新技术。

In this project, to overcome conflicting requirements for the microstructural control of soft-magnetic phase and the alignment of hard-magnetic phase in Sm2Co17/FeCo hybrid nanostructured magnets, a combination of ball milling and High-Pressure Thermal Compression (HPTC) deformation, together with metastable phase transformation strategy, will be carried out. First, Sm-Co amorphous precursor containing uniformly distributed soft-magnetic FeCo phase (< 10 nm in diameter and > 20 wt%) will be produced using ball milling. Then, the amorphous precursor will suffer from the HPTC, and the crystallization transformation and preferential growth of nanoscale SmCo metastable phase in the amorphous matrix will be studied. The formation of textured Sm2Co17 nanograins from the transition of nanoscale oriented SmCo metastable phase will be investigated, with subsequent rapid or low-temperature annealing. Using such strategy, a simultaneous control of the alignment of Sm2Co17 nanograins and the microstructures of FeCo phase will be realized in the Sm2Co17/FeCo hybrid nanostructures. The underlying grain-alignment mechanism for both the nanoscale SmCo metastable phase under the HPTC and the Sm2Co17 nanograins in subsequent annealing processes will be revealed. The interfacial structure of fabricated bulk nanocomposite magnets will be characterized and their magnetic properties will be studied in details. The "processing and compositions - microstructure - magnetic properties" relationships will be achieved. New methods and principles will be developed for creating high-performance hybrid nanostructured magnets.