Degradation processes in Al/SiCp/MgAl2O4 composites prepared from recycled aluminum with fly ash and rice hull ash
✍ Scribed by M. I. Pech-Canul; R. Escalera-Lozano; M. A. Pech-Canul; J. C. Rendón-Angeles; J. López-Cuevas
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- German
- Weight
- 384 KB
- Volume
- 58
- Category
- Article
- ISSN
- 0947-5117
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✦ Synopsis
Abstract
The degradation characteristics of Al/SiC~p~/spinel composites prepared with fly ash (FA) and rice hull ash (RHA) under environmental conditions were investigated. Composite specimens were prepared with recycled aluminum via reactive infiltration in the temperature range 1050–1150 °C for 50–70 min and, in argon atmosphere at a pressure slightly above that of the atmospheric pressure. Results reveal that although both FA and RHA help in preventing SiC~p~ dissolution and the subsequent chemical degradation of the composites, due to the interaction of native carbon in FA with liquid aluminum, FA‐composites are susceptible to corrosion via Al~4~C~3~. Moreover, this phase accelerates the degradation process and increases the damage severity. The primary corrosion mechanism in both types of composites is attributed to microgalvanic coupling between the intermetallic Mg~2~Si and the matrix. Accordingly, an appropriate control of the Si/(Si + Mg) molar ratio in the aluminum alloy hinders the Mg~2~Si corrosion mechanism in both types of composites and a proper FA calcination prevents chemical degradation in FA composites.