Re-investigation of the Phase Equilibria and Thermodynamic Assessment of the Mg-Sm Binary System

Abstract

The Mg-Sm phase diagram has been experimentally studied by x-ray diffraction, scanning electron microscope equipped with energy dispersive spectrometer, and differential scanning calorimetry. Five binary compounds, Mg₄₁Sm₅, Mg₅Sm, Mg₃Sm, Mg₂Sm and MgSm were confirmed to exist in the Mg-Sm system. In addition to Mg₂Sm and MgSm, Mg₃Sm was found to be a congruently melting phase. The Mg₅Sm and Mg₂Sm were found to be only stable at high temperatures and decompose above 400 °C in this work. A special effort was made to determine the extent of the solid solubility ranges of Mg₃Sm, Mg₂Sm, MgSm and, γ-Sm. The Mg-Sm binary system was modeled using the Calphad approach based on new experimental data of this work and all reliable experimental information from literature. A complete thermodynamic description of the Mg-Sm system is obtained and extensive comparisons between calculated and experimental data are presented, indicating that almost all available experimental and theoretical data are fitted satisfactorily.