Phase Equilibria in the Mg - Al - Ca System (Region 50-100 mass% Mg)

Phase equilibria in the ternary system Mg-Al-Ca in the composition range 50-100 mass% Mg were studied by the methods of differential thermal, x-ray diffraction, electron-probe and microscopic analysis. The projection of the liquidus surface on the concentration triangle, isothermal section at 150DGC and polythermal sections at 4.5, 8.5, and 16 mass% Al were constructed. It was determined that additions of Al and Ca decrease the liquidus temperature of magnesium alloys (from 650 to 438DGC). It is shown that the three-phase region < Mg > + < Al2Ca > + < Mg17Al12 > exists at 150DGC with the corresponding two-phase fields. The temperature dependence of the homogeneity range of the Mg-based solid solution was determined, and also the temperatures of the phase transformations which occur in the investigated range of compositions in the system.