The influence of hot-chamber die casting parameters on the microstructure and mechanical properties of magnesium-aluminum alloys containing alkaline elements

The AJ62 magnesium alloy (Mg-6Al-2Sr) is characterized by good creep resistance up to 175°C and good castability enabling production of thin-walled elements in die casting process. The aim of the work was to analyse the influence of hot-chamber die casting parameters on the microstructure and mechanical properties of the AJ62 magnesium alloy. Die casting of investigated alloys was carried out on a 280 tone locking force hot-chamber die casting machine. The piston speed, pressure, die temperature and casting temperature were changed during die casting. The microstructural examinations after die casting showed that the alloy consisted of the solid solution a, lamellar eutectic (Al, Mg) ₄Sr, minor amounts of massive Al ₃Mg ₁₃Sr phase and globular particles of Mn ₅Al ₈. Precipitates of Mg ₁₇Al ₁₂ phase were not detected. The stereological examinations after die casting showed that the volume fraction of massive Al ₃Mg ₁₃Sr phase was dependant on the casting rate. Changing the casting rate had an influence on the volume fraction of (Al, Mg) ₄Sr and Al ₃Mg ₁₃Sr phases. The gas porosity is strongly influenced by the applied pressure and the plunger velocity during die casting process. The mechanical properties of AJ62 magnesium alloy are better at low porosity and high volume fraction of (Al, Mg) ₄Sr phase.