Selective Etching of Sr-Modified and Directionally Solidified Industrial Al-Si Eutectic Alloys for Fabricating Fibrous Eutectic Si

In order to fabricate fibrous eutectic Si, the selective etching of industrial Al-Si eutectic alloys directionally solidified at different growth rates and modified by different amounts of Sr was studied. Flake eutectic and fibrous Si were obtained by selective etching of non-modified, Sr-modified or directionally solidified Al-Si eutectic alloys. The optimal amount of Sr for fabricating branching eutectic Si was 0.04-0.07%. Through directional solidification with a high enough growth rate (more than 200 mu m/s), lamellar eutectic Si transforms to fibrous eutectic Si for use in non-modified Al-Si eutectic alloys. The potentiodynamic polarization and cyclic voltammetry methods were used to test the corrosion behavior of non-modified and Sr-modified Al-Si eutectic alloys. With a constant potential of 0.5 V in HCl solution, non-modified Al-Si eutectic alloys displayed initial pitting corrosion and subsequent spalling corrosion, and 0.04% Sr-modified samples displayed uniform pitting corrosion. Compared with non-modified Al-Si eutectic alloys, Sr-modified samples displayed better corrosion resistance with lower current density and shallower pit depth during the same etching conditions.