Microstructure evolution and precipitation of Al–12Mg alloy solidified under high pressure

The microstructure evolution and precipitation process of Al–12Mg solidified under high pressure were 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. The Mg concentration in the interdendritic region extends up to about 16 wt.%, which is higher than that in the dendrite. Microstructures of sample annealed up to different temperatures indicate that the precipitation process in Al–12Mg solid solution takes place in a non-uniform manner during the heating process, i.e. the β′and β phases are formed in the interdendritic region but no precipitates can be observed in the dendrite.