Critical Systematic Evaluation and Thermodynamic Optimization of the Mn-RE System (RE = Tb, Dy, Ho, Er, Tm and Lu) with Key Experiments for the Mn-Dy System

Abstract

Critical evaluation and optimization of all available phase diagrams and thermodynamic data for the Mn-RE (RE = Tb, Dy, Ho, Er, Tm, and Lu) systems has been conducted to obtain reliable thermodynamic functions of all the phases in the systems. Key experiments for the Mn-Dy system were performed using DSC and solution calorimeter. In the thermodynamic modeling, it is found that the Mn-RE systems show systematic changes in the phase diagrams and thermodynamic properties such as enthalpy of mixing in liquid state in the order of periodic number in the lanthanide series. The systematic thermodynamic modeling approach for RE elements allow to resolve inconsistencies in the experimental data and estimate unknown thermodynamic properties and phase equilibria of Mn-RE system.

Development of thermodynamic database of the Mn‐RE (RE = rare earth metals) binary systems

“…using the modified quasichemical model to describe the liquid phase. Although the assessed Mn‐RE binary phase diagrams are consistent with the experimental data, the experimental heat capacities of the Mn‐RE intermetallic compounds (e.g., Mn 12 Tb, Mn 2 Tb, Mn 23 Lu 6 , Mn 2 Lu, Mn 12 Y, and Mn 2 Y) below 298 K were not taken into account in their assessments [18–20] . Furthermore, in order to develop a compatible thermodynamic database of the multicomponent RE‐Mn‐based alloy systems, the Mn‐RE binary systems still need to be reassessed considering all the experimental information, including phase equilibria and thermodynamic properties.…”

“…Three intermetallic compounds (Mn 12 Tb, Mn 23 Tb 6 , and Mn 2 Tb) were identified by the means of DTA, XRD, XRF, and metallography. However, Kim et al [18–20] . indicated that the results of the invariant reactions determined by Kirchmayr and Lugscheider [34] in the Mn‐Tb binary system are unreliable after comparing with the reported phase equilibria of the Mn‐Nd, Mn‐Gd, and Mn‐Dy binary systems.…”

“…As the sub‐binary systems in the Mn‐RE‐based alloy systems, phase diagrams, and thermodynamic properties of the Mn‐RE binary systems are fundamental to understanding the phase formation, phase stability and phase transformation of the RE‐Mn‐based alloys. The assessments of the Mn‐RE (RE = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho Tm, Lu, and Y) binary systems were performed by Kim et al [18–20] . using the modified quasichemical model to describe the liquid phase.…”

“…Based on the experimental data [41–43] and the reported thermodynamic properties, [40,44,45] thermodynamic calculations of the Mn‐Gd binary system were conducted [20,23,46] . Phase equilibria and thermodynamic properties of the Mn‐Dy binary system were studied by Kichmayr and Lugscheider, [41] Nikolaenko, [47] and Ivanov et al., [40] and thermodynamic calculations of this binary system were carried out by Kim et al., [19] Wang et al., [24] and Wang et al [48] . Phase equilibria of the Mn‐Ho binary system were studied experimentally, [41,47] and were calculated by Wang et al., [49] Kim et al., [20] and Wang et al [24] .…”

Thermodynamic optimization of the Dy–Nd–Fe–B system and application in the recovery and recycling of rare earth metals from NdFeB magnet

“…The only experimental data available in the ternary and quaternary systems are partial phase diagram data at the Fe-rich corner of the Dy-Fe-B system and the section between the ternary magnetic compounds Fe 14 Nd 2 B and Fe 14 Dy 2 B. As highlighted in previous studies, 8,[10][11][12][13] the similarities and regularities in REcontaining systems can be used to predict phase diagram and thermodynamic data where no data are available. In the second part of this study, simulation of the RE extraction process from the Nd-Dy-Fe-B magnet by a liquid metal solvent is performed using the developed thermodynamic database.…”