Chapter 48. Theoretical and Experimental Analysis of Al2O3/Al-Si Composites Processed from Al-Si-Zn and Ai-Si-Mg by Direct Metal Oxidation
- John B. Wachtman Jr.
Published Online: 26 MAR 2008
Copyright © 1992 The American Ceramic Society
Proceedings of the 16th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 13, Issue 7/8
How to Cite
Kharri, S. C. and Koczak, M. J. (1994) Theoretical and Experimental Analysis of Al2O3/Al-Si Composites Processed from Al-Si-Zn and Ai-Si-Mg by Direct Metal Oxidation, in Proceedings of the 16th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 13, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470313954.ch48
- Published Online: 26 MAR 2008
- Published Print: 1 JAN 1994
Print ISBN: 9780470375174
Online ISBN: 9780470313954
An experimental and theoretical study was conducted to study the growth mechanism of the Al2O3lAl-Si composites. Three different A1–5 wt % Mg alloys with silicon content of 2,5 and 10 wt % were evaluated for the growth process at 1573 K. The oxidizing atmosphere was also changed to vary the oxygen partial pressure from 0.1 to 05. The growth rates were monitored by measurement of weight gain during the oxidation process. The growth rates increased with increasing oxygen partial pressure for alloys with lower silicon content. No significant growth rate change was observed for Al-10Si-5Mg alloy with change in oxygen partial pressure. A microstructural and chemical analysis of Al2O3lAl-Si composites fabricated by direct metal oxidation method was conducted. The structure consisted of interconnected network of a- Al2O3 and Al-Si alloy. A thin layer of MgO was observed at the growth surface of the ceramic/metal. Higher growth rates and/or long processing times resulted in increased porosity due to coalescence of alumina grains leaving voids and/or depletion of the metal from the interconnected network. X-ray analysis showed the interconnected alumina network to be predominantly growing in the 〈001〉 direction. The metal alloy was found to be a silicon rich phase. The X-ray and EPMA analysis also showed presence of higher amounts of Si and Mg near the surface. A model is proposed to examine the key steps in the DIMOXTM process in which formation of spinel, transportation of molten alloy and diffusion of aluminum and oxygen are analyzed.