Phase relationship in the Mg-rich corner of the Mg-Zn-Gd ternary system at 400-475 °C

Phase relationship in the Mg-rich corner at 400-475 degrees C of the Mg-Zn-Gd ternary system has been investigated in detail by using electron probe microanalysis (EPMA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) measurements. At 400 degrees C, the Z, I, F, and W phases are all in equilibrium with alpha-Mg. When the temperature rises to 440 degrees C, the Z and I phases are no longer in equilibrium with alpha-Mg. Only the W phase can coexist with alpha-Mg when the temperature reaches 475 degrees C. The four-phase peritectic eutectic transformations F+ liquid -> alpha-Mg+ I and W+ liquid -> alpha-Mg + F occur at 427.5 degrees C and 448 degrees C, respectively. The compositions of the Z, I, F, and W phases are Mg(64.2-64.3 at%)Zn-(7.4-8.0 at%)Gd, Mg-(57.9-58.7 at%)Zn-(8.7-9.1 at%)Gd, Mg-(59.8-63.4 at%)Zn(13.8-14.4 at%)Gd, and Mg-(49.7-50.7 at%)Zn-(24.2-25.5 at%)Gd, respectively. The solubility of Gd in the alpha-Mg solid solution is dramatically decreased by the addition of Zn when the Z, I, F, W/alpha-Mg phases are in equilibrium, quite different from the case of Mg-Gd binary system. (c) 2021 Published by Elsevier B.V.

Automated summary

Investigation of phase relationships in the Mg-rich corner of the Mg-Zn-Gd ternary system at 400-475 degrees C reveals changes in equilibrium states, coexistence phenomena, and peritectic eutectic transformations. The compositions of the Z, I, F, and W phases and the solubility of Gd in the alpha-Mg solid solution are significantly affected by the addition of Zn when the phases are in equilibrium.