Rare-earth oxide coating for sub-micro particulates reinforced aluminum matrix composites

The wettability of sub-micro alumina particulates by aluminum in squeeze-casting alumina reinforced 6061Al composites is poor. The fine particles are prone to cluster in aluminum liquid. The properties of composite are far lower than the theoretical values. To disperse the particles uniformly and to improve the material properties, a liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. TEM observations of coating morphology and microstructure of the composite indicate that Y2O3 was successfully coated on Al2O3 particle surfaces, and the coated powders distributed uniformly in the aluminum liquid. The wettability of the powder by the matrix is improved because of the interfacial reaction of Y2O3 with Al. The mechanical properties of the coated-Al2O3p/6061Al composites are also improved. In the composite (as cast) with 30% volume fraction particles, the ultimate tensile strength increased by 29.8%, the yield strength by 38.4% and the elongation by 10.3%. They reached 457.7 MPa, 215.7 MPa and 1.18%, respectively. The fracture surface presents ductile fracture features.