Study of the thermal stability of phases in the Mg-Al system

A part of the Al-Mg phase diagram was studied in the range of composition between 48 and 61 at.% Al by DSC and SEM/EDS methods. The temperature ranges of stability of the beta, gamma, and epsilon, phases were considered. It was found that the congruent melting temperature of the beta phase was 450 +/- 1 degreesC. The Al content in that phase was determined to be 61 +/- 1 at.% Al at 420 degreesC. The upper temperature limit of the stability of the F phase was established to be 427 +/- 1 degreesC. The Al content changed from 54 at.% at 390 degreesC to 56 at.%, at 420 degreesC. The lower temperature limit of the epsilon phase formation was not determined, as a result of a slow epsilon = beta + gamma reaction. The hypothetical lambda or zeta phases were not found, but it was observed that decomposition of oxides might produce extra thermal effects.