Prediction of the Rem–Fe–Co Phase Diagrams in Melting-Crystallization Region

• Published in: Powder metallurgy and metal ceramics 2022-05, Vol.61 (1-2), p.77-106
• Main Authors: Fartushna, Iu.V., Bulanova, M.V.
• Format: Article
• Language: English
• Subjects: Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Cobalt; Comparative analysis; Component reliability; Composites; Crystal structure; Crystallization; Crystals; Enthalpy; Glass; Intermetallic compounds; Iron; Liquidus; Materials Science; Melting; Metallic Materials; Natural Materials; Phase diagrams; Physicochemical Materials Research; Rare earth metals; Reliability analysis; Samarium; Solidus; Structure
• ISSN: 1068-1302; 1573-9066
• DOI: 10.1007/s11106-022-00297-7

The crystal structures of compounds and phase diagrams of both binary REM–Fe and REM–Co and ternary Fe–Co–REM systems were analyzed and systematically compared. This allowed the nature of physicochemical interaction of components in unstudied systems to be predicted and the reliability of existing experimental data to be evaluated. Based on regular variation of the REM–Fe and REM–Co phase diagrams along the lanthanide rows, typical features that define their liquidus configuration were formulated. According to this characteristic, the REM–Fe and REM–Co systems were divided into six and five types, respectively. Each type was characterized by the presence, number, and composition of congruent compounds. Linear correlations of the temperatures of the same-type invariant equilibria with the melting temperatures of REMs allowed estimating the temperatures of both eutectic equilibria and congruent melting of intermetallics in the unstudied Pm–Fe and {Pm, Tb, Tm, Lu}–Co systems. Based on linear correlations of the standard enthalpies of formation for R 2 Co 17 , RCo 5 , and RCo 3 intermetallics with REM atomic numbers, more reliable values of the enthalpies were identified among the great number of scattered published data and missing values were estimated. The most typical features of the ternary phase diagrams were defined based on a comparative analysis of the REM–Fe and REM–Co phase diagrams and limited published data on phase relations in the REM–Fe–Co systems. The general features of the REM–Fe–Co phase diagrams enabled prediction of the solidus projections for the unstudied systems. Phase regions of the solidus surfaces observed in all systems, except for La–Fe–Co, were established. The solidus temperatures of these regions were estimated for the unstudied systems and experimentally verified on systems with samarium and terbium. The experimental results showed good agreement with the predicted values. Based on the solidus projections, liquidus projections were proposed.