Processing and Microstructure Development in Alumina–Silicon Carbide Intragranular Particulate Composites

Alan Piciacchio, Sang‐Ho ‐H Lee, Gary L. Messing

Research output: Contribution to journalArticle

57 Scopus citations

Abstract

Al2O3–SiC particulate composites were fabricated by hot‐pressing mixtures of 5–30 vol% SiC with either α‐Al2O3, γ‐Al2O3, or boehmite (γ‐AlOOH) to determine whether grain growth or the α‐alumina phase transformation could be used to fabricate intragranular particulate composites. Samples starting with α‐alumina resulted in primarily intergranular SiC of 0.3 μ and an alumina grain size of 1.5–4.1 μm. Heat treatments resulted in SiC coarsening but no entrapment of SiC by grain boundary breakaway. The α‐alumina transformation in the samples starting with γ‐alumina resulted in the entrapment of ∼48% of the 5 vol% of SiC added whereas 79% of the SiC was entrapped in the α‐alumina grains in samples starting with boehmite. Only SiC particles ≤0.2 SmUm were entrapped in the α‐alumina grains during the phase transformation. With increasing SiC content, the relative volume of intragranular SiC decreased, but the amount of intragranular SiC was constant and independent of the amount of SiC added before transformation. The formation of intragranular composites from γ‐alumina and boehmite samples was explained with a model that attributes particle entrapment to the vermicular growth of α‐alumina into the transition alumina matrix during the α‐alumina phase transformation. Seeding the boehmite‐based samples did not affect the concentration of entrapped SiC, but did lower the hot‐pressing densification temperature by as much as 150°C.

Original languageEnglish (US)
Pages (from-to)2157-2164
Number of pages8
JournalJournal of the American Ceramic Society
Volume77
Issue number8
DOIs
StatePublished - Aug 1994

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

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