富铁2:17型Sm-Co基永磁合金的相分解机制与高性能化研究

兼具高磁能积、高矫顽力和高工作温度的永磁材料一直是先进工业领域的发展目标，理论磁能积高达60MGOe的富铁2:17型SmCoFeCuZr高温永磁合金已成为该类材料的首选研发对象。但是，当Fe含量超过20wt.%时合金中难以形成完整的纳米胞状组织，从而导致矫顽力和方形度急剧恶化，使磁能积远低于理论值。研究表明，其相分解形成胞状组织的过程可能同时涉及扩散型相变和位移型相变。本项目拟深入研究富Fe（>20wt%）SmCoFeCuZr合金胞状组织形成过程中层错、位错和空位等缺陷的动态演化及缺陷对溶质原子再分配和结构转变的作用规律，阐明两种相变机制的关联机理。通过深入研究Fe含量引起的相变热力学和动力学差异，掌握富Fe合金的显微组织演变规律，进而优化时效时间和温度以突破相变动力学限制，通过促进1:5胞壁相的析出来构筑完整的纳米胞状组织，为高性能富铁Sm-Co基永磁材料的研发及应用奠定理论与技术基础。

Permanent magnets with large energy product, high coercivity and high working temperature have been highly desired for advanced industrial applications for over decades. The Fe-rich SmCoFeCuZr 2:17-type high temperature permanent magnets with theoretical maximum energy product (BH)max as high as 60 MGOe have been the most promising potential candidates to meet this critical requirement. However, the magnets with Fe content over 20wt.% are difficult to form complete cellular nanostructure, thus deteriorating seriously the coercivity and squareness factor and leading to much lower-than-theoretical (BH)max. The literatures suggested that the decomposition into the cellular nanostructure of the 2:17-type SmCoFeCuZr permanent magnets may evolve both diffusive and displacive phase transformations. However, how the coupled phase transition influence the cell growth and precipitation of the 1:5H cell boundary phase remains unclear. Therefore, the present proposal will focus on the gradual formation and dissociation of the defects including basal stacking faults, dislocations and vacancies during the decomposition transformation of the magnets, and systemically investigate the effects of defects on the solute atom redistributions and phase transformation. Through investigating the Fe content induced differences in thermodynamics and kinetics of the decomposition phase transformation, we shall reveal the detailed microstructural evolution process of the Fe-rich magnets. Next, we shall optimize the aging temperature and time to overcome the kinetic limitation to promote the precipitation of 1:5H cell boundary phase and to construct homogeneous and complete cellular nanostructure in the Fe-rich magnets, so that the magnetic properties can be maximized. The present proposal will provide important theoretical and technical basis to achieve high magnetic performance in the Fe-rich SmCoFeCuZr 2:17-type permanent magnets, which may promote their engineering applications.