Abstract:In situ (Mg₂Si+MgO)/Mg composites fabricated from AZ91-Al₂(SiO₃)₃ under high-energy ultrasonic field were investigated by XRD, DSC and SEM. The results indicate that the size, morphology and distribution of the in situ Mg₂Si particles are greatly optimized with the assistance of the high-energy ultrasonic field. The amounts of the in situ Mg₂Si particles are increased, the sizes are refined, the distributions become uniform, and the morphologies are changed to smooth olive-shape or spherical shape. The amounts of brittle β-Mg₁₇Al₁₂ phases are decreased and the morphologies are granulated. The values of the tensile strength σ_b and HB hardness are increased. These are due to the cavitation effects and acoustic streaming effects induced by the high-energy ultrasonic field.

Key words: in situ composites; high-energy ultrasonic field; morphology; microstructure; mechanical property