LASER PROCESSING TO CREATE IN-SITU AL-SICP SURFACE METAL-MATRIX COMPOSITES

When SiC particulate (SiCp) is preplaced on an aluminium alloy surface, a molten zone can be formed in the aluminium specimen by laser processing, and there is a possibility of producing an in-situ Al-SiCp metal matrix composite (MMC) layer on the surface, which will modify the surface properties. Under specific laser processing conditions in the present work, a smooth and continuous Al-SiCp MMC layer was developed on the surface with well-distributed and embedded SiCp in the layer. In most cases, the SiCp partially dissolved in the liquid and reprecipitated during the solidification. The dissolution of the SiCp is discussed, and the precipitate in the present work is identified as Al4SiC4. The thickness of the Al-SiCp MMC layer was limited to 30-50 mu m when SiCp was preplaced on the specimen. The mechanism of both the formation of the Al-SiCp and the limitation of the MMC layer thickness in this process was studied.