To further understand the underlying physical mechanisms of dealloying of multiphase alloys and control dissolution processes among different phases, the dealloying behavior of melt-spun Al 40 atom % Cu alloy comprising Al2Cu and AlCu intermetallic compounds in a 10 wt % sodium hydroxide (NaOH) aqueous solution was studied. The microstructure of as-dealloyed samples was characterized using x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray analysis. The experimental results show that the alloy with the amount of Al2Cu comparable to that of AlCu can be partially dealloyed, which eventually results in the formation of a unique kind of nanoporous copper/AlCu composite. Additionally, the formation mechanism has been well established to describe the morphology and composition evolutions during the dealloying process based upon kinetic competitions between dissolution of Al atoms and diffusion-rearrangement of Cu atoms, which includes three stages, sequentially, defined as "Al2Cu dealloying," "AlCu dealloying," and "coarsening accompanying underlying AlCu re-dealloying." (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3511771] All rights reserved.