Experimental study of the crystal structure of the Mg15 − xZnxSr3 ternary solid solution in the Mg–Zn–Sr system at 300 °C

A new ternary compound, Mg15 − xZnxSr3 with extensive solid solubility in the Mg–Zn–Sr system was observed and studied using electron probe microanalysis (EPMA), scanning electron microscopy SEM, and X-ray techniques. The solid solubility limits of this compound were found to be Mg15 − xZnxSr3 (0.24 ≤ x ≤ 10.58, at.%) at 300 °C using a diffusion couple and several equilibrated alloys. Analysis of the X-ray diffraction (XRD) patterns was carried out by Rietveld method. XRD data has shown that this solid solution crystallizes in the hexagonal P63/mmc (194) space group with the Ni11Si4Sc3 prototype. The lattice parameters decrease linearly with decreasing Mg content indicating substitutional solid solubility. The fractional atomic occupancy of the 6h, 6g, 4f, 2b and 12k sites of this compound are function of Mg content. Keywords: Ternary compound, Mg alloys, Phase diagram, Crystal structure, X-ray, SEM/EDS, EPMA