Contribution a la caracterisation de l'alliage magnesium-5% aluminum-2% strontium (AJ52x) et son comportement a haute temperature (French text).

摘要

The objectives of this project were the characterisation of the magnesium alloy AJ52x (Mg-5%Al-2%Sr), developed by Noranda, and the study of its behaviour at elevated temperature.; X-ray diffraction measurements taken on the interrupted creep experiment test specimens and on specimens heat treated at 150°C did not indicate any variation of the lattice parameters with time for the magnesium matrix and the Al4Sr lamellae.; X-ray spectrometry analysis on thin foils obtained using electrochemical polishing of the AJ52x creep test specimens revealed variation of the composition of phases in the alloy. The aluminium content of unknown phase changed from 19.1% in the as-cast alloy to 30.9% after 4000 hours of creep testing. Homogenisation of the aluminium content at the grain boundaries was also observed: while a coring phenomenon occurs at the grain boundaries in the as-cast alloy, the aluminium content in the matrix increased slightly after 4000 hours of creep testing and no coring was observed.; The AJ52x alloy shows not only a superior creep resistance when compared to other magnesium alloys, it also possesses good mechanical properties, good corrosion resistance and good castability. These characteristics makes the AJ52x alloy an excellent choice for applications in the automotive industry. (Abstract shortened by UMI.)