A series of Al-Cu alloys were prepared using spark plasma sintering by adjusting the initial composition ratio and powder sizes. The resulting phase and microstructure in these samples were investigated by X-ray diffraction, as well as energy-dispersive spectroscopy and electron back-scatter diffraction of samples examined in the scanning electron microscope. Both the initial composition ratio and powder size affect the phase composition and phase distribution of the sintered samples. Smaller size powders lead to formation of near-equilibrium phase structures, while larger initial powders lead to metastable microstructures containing phases that deviate significantly from the phase diagram. Dealloying of a metastable microstructure was observed to result in the formation of hierarchical skeleton nanoporous Cu structure.