High-Pressure Phase Diagram of Mg-Al Alloys and Variation of Mechanical Properties in Solid Solutioning and Aging Process

The high-pressure phase diagram of a magnesium-rich Mg-Al alloy at a 5.4GPa pressure was investigated. To determine the equilibrium state under high-pressure and high-temperature conditions, the quenching method was applied and a phase analysis of the sample was performed using X-ray diffraction and microscopic observations. The resultant solid solubility of aluminum in magnesium was subsequently increased up to 20at% and the eutectic temperature up to 500°C. The variations of elastic moduli and micro-Vickers hardness for supersaturated Mg-Al solid-solutions against the aluminum concentration and during isochronal ageing were measured. Especially, the attractive increase in hardness for Mg-20at%Al solid solution was observed. Hardness per unit density after ageing at 120°C for 3h increased more than those of extra super duralumin A7075 and Ti-6Al-4V.