Phase equilibria in Mg-Y-Al alloys

Investigations were carried out to determine the character and the temperature of non-variant equilibria in the Mg-Y-Al system alloys containing up to 20 % Y and 20 % Al. The combined solubility of yttrium and aluminium was determined in solid magnesium, a polythermic section at constant magnesium content of 80 % and three isothermic sections at 500, 400 and 300 deg C were plotted in the process. The investigation was carried out using differential thermal, microstructural and micro-X-ray-spectral analysis methods as well as the determining of the mechanical properties. It was shown that two invariant peritectic equilibria occur in the magnesium corner of the system. It was found that small quantities of aluminium (up to 0.5 %) effect favourably the strength of the Mg-Y alloys