Microstructure evolution of Al-Mg alloy during solidification under high pressure

The microstructure of Al-21.6Mg alloy solidified under high pressure was investigated. The results show that the amount of β-Al₃Mg₂ phase decreases with increasing pressure and a supersaturated Al(Mg) solid solution is formed under 2 GPa. The distribution of Mg in the solid solution is inhomogeneous, causing peak asymmetry of the XRD patterns under high pressures. The Mg concentration in the interdendritic region extends up to about 30 at.%, which is higher than that in the dendrite. Besides solution treatment, mechanical alloying, mechanical deformation of pre-alloy ingots and rapid solidification, solidification under high pressure is proved to be a new way to prepare supersaturated Al(Mg) solid solution.