Investigation of the Mg-Rich Part of the Mg-Dy-Sm Phase Diagram

Abstract

Constitution of the Mg-rich part of the ternary phase diagram of Mg with two rare-earth metals, Mg-Dy-Sm was experimentally investigated for the first time using optical and scanning electron microscopy (SEM) with electron probe microanalysis (EPMA), x-ray diffraction and differential thermal analysis. In equilibrium with Mg solid solution only two solid phases were found, each of them being the riches by Mg compound in the respective binary systems, Mg24Dy5 and Mg41Sm5. Each of these compounds can also dissolve some other rare-earth metal. There is significant combine solubility of Dy and Sm in Mg solid solution, which decreases with lowering temperature. In the studied part of the Mg-Dy-Sm system one invariant four-phase equilibrium of L + (Mg24Dy5) ⇆ (Mg) + (Mg41Sm5) exists, which takes place at 535 °C. A number of isothermal partial sections and one temperature-composition section of the Mg-Dy-Sm phase diagram were constructed.