A new aluminium silicon carbide formed in laser processing

During laser processing to create an Al–SiCp surface metal matrix composite (MMC) layer on AA6061 Al alloy, needle-shaped particles were formed when a high laser energy input was used. Optical microscopy showed this phase to be similar to Al4C3 and Al4SiC4. Previous work was unable to identify the compound as one of those already known in the Al–Si–C system that included Al4C3, Al4SiC4, Al8SiC7, Al4Si2C5 and Al4Si3C6. Therefore, in the present work a phase identification was undertaken on the unknown, using transmission electron microscope (TEM) and the associated energy dispersion analytical X-ray (EDAX) system, together with X-ray diffractometry (XRD). This suggested that the phase was an aluminium silicon carbide having an hexagonal structure with a = 0.3316 and c = 2.1330 nm, which could be a metastable phase formed under the particular laser processing conditions used.