高丰度稀土永磁合金相平衡及微观组织与磁性能研究

In this project, microstructure and magnetic properties of permanent alloys containing abundant rare elements (e.g. La, Ce, Y) are studied using thermodynamic calculation and diffusion kinetic modeling with the key alloy experiments. Phase equilibira of the RE-Fe-B(RE=La,Ce,Y) ternary systems including isothermal sections at different temperatures, vertical sections and liquidus projections are measured experimentally through key alloy experiments and diffusion couple technique. Thermodynamic parameters of all phases in the RE-Fe-B ternary systems are optimized based on the measured phase diagram data and thermodynamic information using the CALPHAD method and then thermodynamic database of the RE-Fe-B ternary systems are developed. On the other hand, using diffusion couple technique with electronic microprobe analysis (EMPA), interdiffusion coefficients of components in the RE-Fe-B(RE=La,Ce,Y,Nd) alloys were determined by means of the Boltzmann-Matano method. Through thermodynamic calculation and diffusion kinetic modeling using thermodynamic parameters and diffusion data, stable/metastable phase equilibira information on multi-component RE-Fe-B alloys and the relation of phase composition with temperature and time were obtained, which is fundamental to design and prepare novel Nd-Fe-B based permanent alloys containing abundant rare elements such as La, Ce and Y. Furthermore, structural transitions and intrinsic magnetic properties such as coercivity, remanent magnetization and maximum energy product of Nd-Fe-B alloys containing abundant rare elements are studied. Based on the thermodynamic calculation and diffusion kinetic modeling of the RE-Fe-B alloys, the relationships among the composition, crystal structure, phase transformation and magnetic properties of the alloys are elucidated, which is fundamental and of importance for developing novel Nd-Fe-B based permanent materials containing abundant rare elements.

结合广西稀土矿产资源优势，针对储量丰富的La、Ce、Y等高丰度稀土在永磁材料中的有效应用，推动稀土资源的平衡高值利用，本项目采用关键实验与热力学计算相结合的方法，测定高丰度稀土RE-Fe-B(RE=La, Ce, Y)合金的相平衡，确定高丰度稀土RE-Fe-B合金体系的相图热力学参数。采用扩散偶技术、电子探针微区成分分析及Boltzmann-Matano方法，测量高丰度稀土RE-Fe-B(RE=La, Ce, Y, Nd)合金中相关相的互扩散系数。利用获得的相图热力学参数和扩散动力学参数，计算多元高丰度稀土合金的稳定/亚稳相平衡信息以及合金中各相的成分随温度和时间的变化关系，设计制备高丰度稀土永磁合金样品，在实测合金样品的相结构、相转变、微观组织及内禀磁性能的基础上，探讨合金成分、微观组织结构与合金磁性能的相互作用关系，为研究开发高性能的高丰度稀土永磁材料提供实验数据和理论依据。

针对储量丰富的La、Ce、Y等高丰度稀土在永磁材料中的有效利用，推动稀土资源的平衡高值利用，本项目采用采用关键实验（合金与扩散偶）和理论计算（热力学计算和扩散动力学模拟）相结合的方法，测定了稀土RE-Fe、RE-B、RE1-RE2、RE-Fe-B、RE1-RE2-Fe（RE=La, Ce, Pr, Nd, Y）等二元体系、三元体系关键合金样品的相变温度、相组成和相成分，确定了稀土La-Fe-B、Ce-Fe-B、Pr-Fe-B、Y-Fe-B、La-Nd-Fe、La-Ce-Fe、La-Pr-Fe、Ce-Nd-Fe、Ce-Pr-Fe等三元体系不同温度和成分条件下的等温截面和垂直截面以及合金中化合物的晶体结构、相转变、热力学稳定性等信息，构筑了上述三元合金体系的相图，热力学优化计算了稀土RE-Fe-B合金体系中19个二元体系和10个三元体系相图，获得了合理、可靠和自洽的稀土RE-Fe-B合金体系中相关二元体系、三元体系的热力学参数，构建了完善的高丰度稀土RE-Fe-B（RE=La, Ce, Pr, Nd, Y）永磁合金体系相图热力学数据库。基于文献报道的Nd-Fe-B合金体系中各类扩散系数信息，动力学优化计算了Nd、Fe、B在液相和fcc相中的原子移动性参数，建立了Nd-Fe-B合金体系中液体和fcc相的扩散动力学数据库。根据本项目构建的稀土RE-Fe-B合金体系相图热力学数据库及化合物结构信息，通过相平衡计算，设计和制备了一系列不同成分和工艺条件下的稀土RE-Fe-B永磁合金快淬样品，分析表征了快淬合金样品的相组成、相结构和微观组织，实验测试了稀土RE-Fe-B快淬合金的矫顽力、剩磁、最大磁能积等磁性能。利用已获得的稀土Nd-Fe-B合金体系相图热力学数据库和扩散动力学数据库，采用DICTRA模拟软件，计算模拟了不同冷却速率（轮速）下Nd-Fe-B合金中主相Nd2Fe14B和α-Fe相的形成规律和相含量的变化规律，阐明了高丰度稀土RE-Fe-B永磁合金成分、制备工艺、微观组织结构与磁性能的相互作用关系，为研发低成本高性能高丰度稀土永磁材料提供了科学依据，推动了稀土资源的高效高值利用。