| Tartalmi leírás: |
Metal matrix composites reinforced by ceramic hollow microspheres were produced as special porous metals, called metal matrix syntactic foams (MMSFs). In this paper the microstructure of the ceramic hollow microspheres as reinforcing element was investigated in connection with the production of MMSFs by pressure infiltration. SL150 and SL300 type ceramic microspheres from Envirospheres Ltd. (Australia) were investigated. They contained various oxide ceramics, mainly Al2O3 and SiO2. The chemical composition and the microstructure of the microspheres had strong effect on their infiltration characteristics; therefore in the view of MMSF production it was very important to know microstructural details about the microspheres. Due to this energy dispersive X-ray spectroscopy maps were recorded from the cross sections of the microspheres? wall. The results showed that the Al2O3 and SiO2 distribution was not equal; the Al2O3 phase was embedded in the surrounding mullite and SiO2 phase in the form of needles. Line energy dispersive X-ray spectroscopy measurements were performed in order to investigate the possible reaction between the different aluminium alloy matrices and the ceramic microspheres. The results showed that, due to the uneven distribution of Al2O3 rich particles, the molten aluminium could reduce the SiO2 rich parts of the microspheres and the wall of the hollow microspheres became damaged and degraded. This chemical reaction between the microspheres and the walls could make the infiltration easier, but the resulting mechanical properties will be lower due to the damaged microsphere walls.
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