Interfacial Microstructure Formed by Reactive Metal Penetration of Al into Mullite

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Microstructures in the reaction interface between molten Al and dense mullite have been studied by transmission electron microscopy to provide insight into mechanisms for forming ceramic-metal composites by reactive metal penetration. The reactions, which have the overall stoichiometry, 3Al{sub 6}Si{sub 2}O{sub 13} + (8 + x)Al {r_arrow} 13Al{sub 2}O{sub 3} + xAl + 6Si, were carried out at temperatures of 900, 1100, and 1200 C for 5 minutes and 60 minutes, and 1400 C for 15 minutes. Observed phases generally were those given in the above reaction, although their proportions and interfacial microstructure differed strongly with reaction temperature. After reaction ... continued below

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27 p.

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Du, T.B.; Ewsuk, K.G.; Fahrenholtz, W.G.; Loehman, R.E. & Lu, P. March 3, 1999.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

Microstructures in the reaction interface between molten Al and dense mullite have been studied by transmission electron microscopy to provide insight into mechanisms for forming ceramic-metal composites by reactive metal penetration. The reactions, which have the overall stoichiometry, 3Al{sub 6}Si{sub 2}O{sub 13} + (8 + x)Al {r_arrow} 13Al{sub 2}O{sub 3} + xAl + 6Si, were carried out at temperatures of 900, 1100, and 1200 C for 5 minutes and 60 minutes, and 1400 C for 15 minutes. Observed phases generally were those given in the above reaction, although their proportions and interfacial microstructure differed strongly with reaction temperature. After reaction at 900 C, a thin Al layer separated unreacted mullite from the {alpha}-Al{sub 2}O{sub 3} and Al reaction products. No Si phase was found near the reaction front. After 5 minutes at 1100 C, the reaction front contained Si, {alpha}-Al{sub 2}O{sub 3}, and an aluminum oxide phase with a high concentration of Si. After 60 minutes at 1100 C many of the {alpha}-Al{sub 2}O{sub 3} particles were needle-shaped with a preferred orientation. After reaction at 1200 C, the reaction front contained a high density of Si particles that formed a continuous layer over many of the mullite grains. The sample reacted at 1400 C for 15 minutes had a dense {alpha}-Al{sub 2}O{sub 3} reaction layer less than 2 {micro}m thick. Some isolated Si particles were present between the {alpha}-Al{sub 2}O{sub 3} layer and the unreacted mullite. Using previously measured reaction kinetics data the observed temperature dependence of the interfacial microstructure have been modeled as three sequential steps, each one of which is rate-limiting in a different temperature range.

Physical Description

27 p.

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OSTI as DE00004182

Medium: P; Size: 27 pages

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  • Journal Name: Journal of Materials Research; Other Information: Submitted to Journal of Materials Research

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  • Report No.: SAND99-0533J
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 4182
  • Archival Resource Key: ark:/67531/metadc681283

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • March 3, 1999

Added to The UNT Digital Library

  • July 25, 2015, 2:20 a.m.

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  • April 10, 2017, 6:40 p.m.

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Du, T.B.; Ewsuk, K.G.; Fahrenholtz, W.G.; Loehman, R.E. & Lu, P. Interfacial Microstructure Formed by Reactive Metal Penetration of Al into Mullite, article, March 3, 1999; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc681283/: accessed November 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.