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

Abstract

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 μm/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.