Dealloying behavior of dual-phase Al 15 at.% Cu alloy in an acidic solution

To further understand the underlying physical mechanisms of dealloying of multi-phase alloys, dealloying behavior of melt-spun Al 15 at.% Cu alloy comprising α-Al solid solution and Al ₂Cu intermetallic compound in a 5 wt.% hydrochloric acid (HCl) aqueous solution was investigated. The microstructure of as-dealloyed samples was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and transmission electron microscopy. The experimental results show the Al-Cu alloy with the amount of α-Al comparable to that of Al ₂Cu can be completely dealloyed, which eventually results in the formation of nanoporous copper (NPC) with a homogeneous porous structure, while during which two other kinds of nanoporous structures can be sequentially obtained for different dealloying times. The formation mechanism has been well established to describe the morphological and compositional evolutions during dealloying process based upon kinetic competitions between dissolution of Al atoms and diffusion-rearrangement of Cu atoms, which includes three stages orderly defined as "α-Al dealloying," "Al ₂Cu dealloying," and "coarsening of NPC in porous pore walls".