To develop novel Nd-Fe-B-based permanent magnets with rare earth (RE) metals, phase equilibria and thermodynamic information of multi-component RE-Fe-B-based alloy systems is indispensable. In this work, thermodynamic assessment of the RE-B (RE=Ho, Er, Tm) binary systems as the important binary systems in the RE-Fe-B-based alloy systems were carried out using the CALPHAD (Calculation of Phase Diagram) method. The solution phases including liquid, hcp(α-Ho, α-Er and α-Tm) and rhombohedral(β-B) in the RE-B (RE=Ho, Er, Tm) binary systems are modeled by the substitutional solution model. The intermetallic compounds, HoB₂, HoB₄, HoB₆, HoB₁₂, HoB₆₆, ErB₂, ErB₄, ErB₁₂, ErB₆₆, TmB₂, TmB₄, TmB₁₂ and TmB_66, are treated as the stoichiometric compounds. Self-consistent thermodynamic parameters to describe Gibbs energies of phases in the RE-B (RE=Ho, Er, Tm) binary systems were obtained finally. The calculated results agree well with the reported data.

要开发具有稀土（RE）金属的新型Nd-Fe-B基永磁体，多组分RE-Fe-B基合金体系的相平衡和热力学信息必不可少。在这项工作中，使用CALPHAD（相图计算）对作为RE-Fe-B基合金系统中重要的二元体系的RE-B（RE = Ho，Er，Tm）二元体系进行了热力学评估。方法。用替代溶液模型对RE-B（RE = Ho，Er，Tm）二元系统中的液相，hcp（α-Ho，α-Er和α-Tm）和菱面体（β-B）的溶液相进行建模。金属间化合物HoB ₂，HoB ₄，HoB ₆，HoB ₁₂，HoB ₆₆，ErB ₂，ErB ₄将ErB ₁₂，ErB ₆₆，TmB ₂，TmB ₄，TmB ₁₂和TmB ₆₆视为化学计量化合物。最终获得了描述RE-B（RE = Ho，Er，Tm）二元系统中相的吉布斯能的自洽热力学参数。计算结果与报告数据吻合良好。