Processing and microstructure development in alumina-silicon carbide intragranular particulate composites

Journal Article · Mon Aug 01 00:00:00 EDT 1994 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1994.tb07112.x· OSTI ID:6988229

Piciacchio, A; Lee, S H; Messing, G L ^[1]

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1. Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

Al[sub 2]O[sub 3]-SiC particulate composites were fabricated by hot-pressing mixtures of 5--30 vol% SiC with either [alpha]-Al[sub 2]O[sub 3], [gamma]-Al[sub 2]O[sub 3], or boehmite ([gamma]-AlOOH) to determine whether grain growth or the [alpha]-alumina phase transformation could be used to fabricate intragranular particulate composites. Samples starting with [alpha]-alumina resulted in primarily intergranular SiC of 0.3 [mu]m and an alumina grain size of 1.5--4.1 [mu]m. Heat treatments resulted in SiC coarsening but no entrapment of SiC by grain boundary breakaway. The [alpha]-alumina transformation in the sample starting with [gamma]-alumina resulted in the entrapment of [approximately]48% of the 5 vol% of SiC added whereas 79% of the SiC was entrapped in the [alpha]-alumina grains in samples starting with boehmite. Only SiC particles [le] 0.2 [mu]m were entrapped in the [alpha]-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 [gamma]-alumina and boehmite samples was explained with a model that attributes particle entrapment to the vermicular growth of [alpha]-alumina into the transition alumina matrix during the [alpha]-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.

• OSTI ID: 6988229
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 77:8; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
FABRICATION
MICROSTRUCTURE
COMPOSITE MATERIALS
SILICON CARBIDES
CRYSTAL-PHASE TRANSFORMATIONS
GRAIN GROWTH
ALUMINIUM COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
MATERIALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SILICON COMPOUNDS
360601* - Other Materials- Preparation & Manufacture
360602 - Other Materials- Structure & Phase Studies