Determination of the Phase Equilibria in the Mn-Sn-Zn System at 500 °C

The isothermal section of the Mn-Sn-Zn system at 500 degrees C was determined with 20 alloys. The alloys were prepared by melting the pure elements in evacuated quartz capsules. The alloy samples were examined by means of X-ray diffraction (XRD) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. A new ternary phase Mn4Zn8Sn (lambda) was found to have a bcc structure with a lattice parameter a = 0.92508 (5) nm. Its composition range spans 25 to 35 at. pct Mn, 4 to 8 at. pct Sn, and 55 to 70 at. pct Zn. The Zn is substituted for Mn in Mn3Sn, Mn2Sn, and Mn3Sn2. The solubility of Zn in Mn3Sn, Mn2Sn, and Mn3Sn2 was measured to be about 17, 12, and 4 at. pct, respectively. The phase boundaries of the liquid and beta-Mn phases were well established. The following 3 three-phase equilibria were well determined: (1) beta-Mn + epsilon-MnZn3 + Mn3Sn, (2) lambda + Mn3Sn + Mn2Sn, and (3) L+ lambda + Mn2Sn. The additional 5 three-phase equilibria, which are epsilon-MnZn3 + lambda + Mn3Sn, epsilon(1)-MnZn3 + epsilon-MnZn3 + lambda, epsilon(1)-MnZn3 + lambda + L, Mn2Sn + L + MnSn2, and Mn3Sn2 + MnSn2 + Mn2Sn, were deduced and shown with dashed lines in the present isothermal section.