通过调控晶间相同时提高(Nd,RE)-(Fe,Co)-B (RE=La,Ce,Pr)系稀土永磁合金剩磁和矫顽力的机理研究

在硬磁性晶粒之间形成晶间相是提高Nd-Fe-B永磁材料磁性能的一种有效手段，但其剩磁和矫顽力难以同时提高。本项目将以(Nd,RE)-(Fe,Co)-B (RE=La,Ce,Pr)系合金为对象，研究调控晶间相同时提高该合金的剩磁和矫顽力的机理。通过调整合金成分、优化快淬工艺参数和磁场退火等方法调节晶间相的体积分数和分布。利用球差透射电子显微镜和原子探针层析技术分析晶间相的类型、结构和成分。利用第一性原理计算偏聚原子在晶界处所有可能的占位和偏聚能，结合实验数据分析不同类型晶间相的形成机理。分析合金的磁化曲线、磁滞回线、矫顽力随温度的变化曲线、合金的磁粘滞行为、交互作用曲线和不可逆磁化率随磁场的变化曲线，观察磁畴的相应变化，研究合金的反磁化机制和铁磁交互作用。结合微观结构和磁性能的结果，弄清晶间相同时提高剩磁和矫顽力的机理，为制备开发同时具有高剩磁、高矫顽力的稀土永磁材料打下良好的理论基础。

Formation of the intergranular phase between hard magnetic grains is an effective way to increase the magnetic properties of permanent magnetic materials. However, the remanence and coercivity cannot be improved simultaneously. In this project, the mechanism of enhancing simultaneously the remanence and coercivity of (Nd, RE)-(Fe, Co)-B (RE=La, Ce, Pr) rare-earth permanent magnetic alloys by tuning intergranular phase will be investigated. The fraction and distribution of the intergranular phase will be adjusted by compositional modification of alloys, optimizing melt-spinning parameters and using magnetic field annealing treatment. The spherical aberration corrected transmission electron microscopy (Cs-corrected TEM) and atom probe tomography (APT) will be employed to observe the type, microstructure and chemistry of the intergranular phase. The possible sites on the grain boundary of segregated atoms and the segregation energy will be obtained by first-principles calculations. The magnetization reversal mechanism and magnetic interaction will be investigated by analyzing the magnetization curves, hysteresis loops, the temperature dependence of the coercivity, magnetic viscosity, the magnetic interaction plots, the irreversible susceptibility as a function of magnetic field and changes of domain structure. Combined with results of microstructure and magnetic properties, the mechanism of enhancing simultaneously the remanence and coercivity of (Nd, RE)-(Fe, Co)-B (RE=La, Ce, Pr) rare-earth permanent magnetic alloys by tuning intergranular phase will be explored to provide a theoretical basis to design and develop permanent magnetic materials with high remanence and coercivity.