Thermodynamics and interdiffusion of the Y–Nd, Y–Tb and Tb–Nd systems

Based on the available experimental data reported in the literature, the Y–Nd, Y–Tb and Tb–Nd systems were re-assessed thermodynamically using the CALPHAD (CALculation of PHAse Diagram) method in this work. The calculated phase diagrams of the three binary systems are well consistent with the experimental results. Based on the calculated phase diagrams, 9 solid-solid diffusion couples in hcp phase region were prepared and annealed at 900, 1000, and 1100 °C. The concentration distributions were measured using Electron Probe Microanalysis (EPMA), and the interdiffusion coefficients at different temperatures were evaluated through the Sauer–Freise approach. Subsequently, the CALTPP (CALculation of Thermo-Physical Properties) software was applied to optimize the atomic mobilities as functions of both temperature and composition by integrating the thermodynamic assessment with the experimental diffusion data. The simulated diffusion behavior exhibited good consistency with the experimental results, confirming the reliability of the optimized mobility parameters.