Phase evolution of Mg-Al-Zr nanophase alloys prepared by mechanical alloying

Al-Mg and Al-Mg-Zr alloys were processed by mechanical alloying. The phase constitution of the powders was strongly dependent on the composition of the starting mixture. In as-milled powders, an Al(Mg) solid solution was formed with up to 40 at% Al, which after annealing transformed to the equilibrium β-Al3Mg2 phase. For high Mg concentrations (60-90 at%) the dominant phase was γ-Al12Mg17 in accordance with the equilibrium phase diagram. The addition of Zr led to the appearance of Zr-Al intermetallics causing Mg to precipitate out of the Al(Mg) solution. The effect of zirconium was also to refine the structure and to retard grain growth.