In-situ nanoscale Al₂O₃ spherical particle formation in Al-matrix of Al–Si/SiC_P MMC foil by laser pulsing

Abstract

An excimer pulse laser treatment is gaining more popularity for the surface modification of a metallic material due to its non-equilibrium processing character, ease of process, minimal depth of modification, effective absorptivity and extremely high cooling rate. In the present study, the laser surface treatment of the Al–Si/SiC_P Metal Matrix Composite foil was carried out by pulse excimer laser. The parameter used for the surface modifications are: pulse energy 1980 J m^–2 and number of pulses 1, 5 and 10. The microstructural characterization was carried out by SEM and TEM (Transmission Electron Microscopy), whereas the compositional analysis was done by TEM/EDS (Energy dispersive spectroscopy). The work demonstrates the possibility of in situ formation of fine scale, nano- to sub-micrometer, Al₂O₃ particles in the surface layer of Al-matrix composite. After a pulse of laser is irradiated on the Metal Matrix Composite surface, spherical Al₂O₃ particles are observed to nucleate and grow heterogeneously, whereas after 5 pulses of laser treatment, the fraction of Al₂O₃ particles increased. Later, at 10 pulses, it further increases ~30% of the surface. The particles showed a size distribution, the higher size limit increase with number of pulses, but it remains same around (2–20 nm) for lower range. Transmission Electron Microscopy study indicates the nucleation of the new Al₂O₃ phase with laser pulse cycle concurrent with the growth of the already existing particles.