通过实验和相图计算(calculation of phase diagram, CALPHAD)相结合的方法研究Nd-B-Sm体系的相平衡。基于边际二元相图设计并使用电弧熔炼炉制备7种不同成分的三元合金,通过电子探针显微分析和X射线粉末衍射研究773 K、873 K退火态和铸态Nd-B-Sm合金的相组成。结果表明：由于Nd和Sm的原子半径和电负性相似,Nd-B和Sm-B体系化合物具有相同的晶体结构,Nd2B5和Sm2B5形成了(Nd,Sm)2B5无限固溶体,未发现三元化合物。基于本工作所得相平衡数据和文献中报道的二元体系热力学描述,使用CALPHAD方法对Nd-B-Sm体系进行热力学优化,得到了一组自洽的热力学参数。计算所得773 K和873 K等温截面、液相面投影图、希尔凝固路径与实验数据吻合良好。
Phase equilibria of the Nd-B-Sm system were investigated through a combination of experiments and calculations of phase diagram. Based on the sub-binary phase diagrams, seven ternary alloys with different composition were designed and prepared using an electric arc melting furnace. Phase constituents of the Nd-B-Sm alloys annealed at 773 K, 873 K and in the as-cast state were investigated using electron probe microanalysis and X-ray powder diffraction. The results indicate that due to the similarity in atomic radii and electronegativity between Nd and Sm, the Nd-B and Sm-B compounds share identical crystal structures so that Nd₂B₅ and Sm₂B₅ form an infinite solid solution of (Nd,Sm)₂B₅, with no ternary compounds observed. Base on the phase equilibrium data obtained in this work and thermodynamic description on the binary systems reported in the literature, a set of self-consistent thermodynamic parameters is obtained by thermodynamic optimization of the Nd-B-Sm system using the CALPHAD method. The calculated isothermal sections at 773 K and 873 K, the liquidus projection, and the Scheil solidification path are in good agreement with the experimental data.
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