Selective chemical dealloying for fabrication of surface porous al88cu6si6 eutectic alloy

Al-based alloys have recently attracted considerable interest as structural materials and light weight materials due to their excellent physical and mechanical properties. For the investigation of the potential of Al-based alloys, a surface porous Al₈₈Cu₆Si₆ eutectic alloy has been fabricated through a chemical leaching process. The formation and microstructure of the surface porous Al₈₈Cu₆Si₆ eutectic alloy have been investigated using X-ray diffraction and scanning electron microscopy. The Al₈₈Cu₆Si₆ eutectic alloy is composed of an α-Al dendrite phase and a single eutectic phase of Al₂Cu and a-Al. We intended to remove only the α-Al phase and then the Al₂Cu phase would form a porous structure on the surface with open pores. Both acidic and alkaline aqueous chemical solutions were used with various concentrations to modify the influence on the microstructure and the overall chemical reaction was carried out for 24 hr. A homogeneous open porous structure on the surface was revealed via selective chemical leaching with a H2SO4 solution. Only the α-Al phase was successfully leached while the morphology of the Al₂Cu phase was maintained. The pore size was in a range of 1~5 μm and the dealloying depth was nearly3 μm. However, under an alkaline NaOH, aqueous solution, an inhomogeneous porous structure on the surface was formed with a 5 wt% NaOH solution and the morphology of the Al₂Cu phase was not preserved. In addition, the sample that was leached by using a 7 wt% NaOH solution crumbled. Al extracted from the Al₂Cu phase as α-Al phase was dealloyed, and increasing concentration of NaOH strongly influenced the morphology of the Al₂Cu phase and sample statement.