稀土RE-Mn基合金相图及相关化合物磁性研究

In this project, phase diagrams of the RE-Mn-Si,RE-Mn-Ge and RE-Mn-Sn(RE=Nd,Gd) ternary systems are measured experimentally through the key alloy experiments, including isothermal sections at different temperatures, vertical sections and liquidus projections. Crystal structures and thermodynamic stabilities of the intermetallic compounds in these systems are investigated. Themodynamic parameters of all phases in the RE-Mn-Si,RE-Mn-Ge and RE-Mn-Sn(RE=Nd,Gd)ternary systems are optimized based on the measured phase diagram data and thermodynamic information, and then thermodynamic database of the RE-Mn-Si,RE-Mn-Ge and RE-Mn-Sn ternary systems are developed using the CALPHAD method, which is fundamental to design novel RE-Mn based materials. Furthermore, structural transitions, metamagnetic transition,intrinsic magentic properties and physical properties such as magnetoresistance and magnetocaloric effect of the intermetallic compounds in the RE-Mn-Si,RE-Mn-Ge and RE-Mn-Sn(RE=Nd,Gd) ternary systems are studied. Combined with phase diagrams, crystal structures and thermodynamic stablilities of the intermetallic compounds in the RE-Mn-Si,RE-Mn-Ge and RE-Mn-Sn ternary systems measured in this project, the relationships among the composition, crystal structure, phase transformation and magnetic properties of the intermetallic compounds in these ternary systems are elucidated, which is fundamental and of importance for developing novel RE-Mn based magnetic materials.

针对广西稀土RE、Mn等有色金属矿产资源的有效利用，本项目拟采用关键合金实验与相图计算（CALPHAD）相结合的方法，确定稀土RE-Mn-X（RE= Nd, Gd；X=Ge, Si, Sn）合金的相平衡关系以及合金中化合物的晶体结构、结构转变、热力学稳定性等信息，构筑稀土RE-Mn-Ge、RE-Mn-Si和RE-Mn-Sn三元合金体系的相图，建立稀土RE-Mn基合金体系相图热力学数据库，为稀土锰基磁性功能材料的设计奠定热力学基础。综合本项目实测的合金相图、化合物晶体结构及其热力学稳定性等信息，通过实验测定稀土RE-Mn-Si、RE-Mn-Ge和RE-Mn-Sn(RE=Nd,Gd)体系中化合物的结构转变、磁相变、内禀磁性、磁电阻、磁熵变等性能，探讨合金体系中化合物成分、结构转变与磁性行为之间的相互作用关系，为研究开发新型稀土锰基磁性功能材料提供实验数据和理论依据。

针对广西稀土RE、Mn等有色金属矿产资源的有效利用，本项目实验测定了稀土RE-Mn、RE-Si/Ge（RE=La, Nd, Gd, Dy, Ho）、Mn-In 等9个二元系关键合金样品的相转变温度，测定了Gd-Mn-Si、Gd-Mn-Ge、Nd-Mn-Si及Nd-Mn-Ge三元合金体系不同温度下的相平衡关系以及合金中化合物的晶体结构、结构转变、热力学稳定性等信息，构筑了上述4个三元合金体系的相图。结合本项目获得的相转变信息和文献报道的相图及热力学实验数据，采用相图计算（CALPHAD）方法，完成了9个二元系的相图热力学评估与优化，获得了这些二元体系合理、可靠和自洽的相图热力学参数，为稀土锰基磁性功能材料的设计奠定热力学基础。综合本项目实测的合金相图及化合物晶体结构等信息，实验测定了稀土RE-Mn-Ge (RE = Nd, Gd)、Nd-Mn-X (X= Ge, Si)体系中REMn2X2化合物的结构转变、磁相变、内禀磁性、磁熵变等性能，探讨合金体系中化合物成分、结构转变与磁性行为之间的相互作用关系，为研究开发新型稀土锰基磁性功能材料提供实验数据和理论依据。