Microstructures and Phase Transformation of Al-Rased composite materials Reinforced by Al-Cu-Co Decagonal Quasicrystalline Particles

Al65Cu15Co20 decagonal quasicrystalline alloys were prepared by an arc-melting furnace. The aluminium-based composites were fabricated by using the Al65Cu15Co20 decagonal quasicrystalline particles as reinforcing phase and Al-4.5 wt%Cu alloy as matrix with mechanical stirring. The microstructures, the phase composition, and the distribution of Al65Cu15Co20 were characterisied by XRD, SEM, SEM and EDS for the Al65Cu15Co20 quasicrystalline alloys and the reinforced composites. And the morphology, chemical composition and structure changes of the quasicrystalline particles before and after adding to the melt were also analysised. As the interdiffusion occurs between the quasicrystalline particles and the melt, the quasicrystalline particles can not exist stably in the melt. The morphology of the particles turns from inregular polygons to block and lath-like in shape as following: D-Al62.10Cu17.46Co20.44 -> theta-Al79.55Cu1.10Co19.32 after adding the quasicrystalline particles into the melt. During the solidification process, the theta phase distributes uniformly along the grain boundaries because of the "interfacial pushing effect".