FEASIBILITY OFAl/Al2O3COMPOSITE PARTICLES PREPARED BY SEMI-SOLID MECHANICAL STIRRING METHOD

A discrete coating of aluminum particles on the surface ofAl2O3particles was prepared by the semi-solid mechanical stirring method.Al2O3particles with an average diameter of 80 μm, preheated to about 300°C, were added to semi-solid pure aluminum to prepare a slurry by the mechanical stirring method. The volume fraction ofAl2O3particles in the slurry was about 20%. As the ceramic particles were uniformly dispersed in the semi-solid aluminum, the temperature of the slurry decreased quickly, but the slurry continued to be stirred until all the slurry was converted into composite powder. The composite powder was then cooled down to room temperature in a steel block cooler in an argon atmosphere. The surface morphology and transverse sections of the composite powder were examined using a scanning electron microscope (SEM), electron probe X-ray microanalyser (EPMA), optical microscope and augur electron spectroscopy (AES). The results indicate that the composite powder was a mixture ofAl/Al2O3composite particles and pure aluminum powder in quasi-spherical shapes. A single layer of nano-, submicron- and micron-sized aluminum particles were coated on the surfaces of theAl2O3particles. The slurry could be converted into the composite powder resulting from faster solidification of liquid aluminum and mechanical stirring.