Struktur geschmolzener Magnesium—Cadmium-Legierungen / Structure of Molten Magnesium-Cadmium Alloys

Abstract

Alloys from the system Mg - Cd were investigated in transmission by X-ray diffraction. From the intensity curves radial atomic distribution functions were obtained which allow to find the compound formation in the molten alloys of this system. The discussion of an additional intensity maximum yields the existence of the distance of 5.14 A between two Cd-atoms in the melts with 10 to 60 at.-% Cd. This distance is in agreement with a Cd - Cd-distance in the elementary cell of solid Mg₃Cd. Thus the existence of agglomerates of the composition Mg₃Cd₂ in these melts is demonstrated. It is pointed out that in this system (75 at.-% Mg-25 at.-% Cd) agglomerates exist in the melt which have the same atomic arrangement as the corresponding solid state although a temperature gap of more than 300 °C separates the existence region of the solid state and the solidus. The results are confirmed by mass-spectrometric investigations which show that also the vapour phase of Mg₃Cd contains molecules of the composition Mg₃Cd₂ . The importance of mass-spectrometric information for the confirmation of structural investigations of melts and amorphous solids is shown.