Extended solubility in the electrodeposited nanocrystalline Al-Mg alloy dendrites

摘要

Nanocrystalline, supersaturated and metastable Al-Mg dendrites with stacks of smooth and rough globules were produced through electrodeposition. Rough globules always formed over the smooth ones. The smooth globules possessed face centered cubic (fcc)-AI(Mg) phase with -20at.% Mg. The rough globules contained ~80at.% Mg and corresponded to hexagonal close packed (hcp)-Mg(Al) phase. Across the smooth-rough boundary a drastic jump in the composition from -20 to -80 at.% Mg was observed in nanometer scale. The metastable equilibrium between the supersaturated fee and hep phases was explained using the estimated free energy change-composition (AG-x) curves.