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Effects of α‐Sic versus β‐Sic Starting Powders on Microstructure and Fracture Toughness of Sic Sintered with Al 2 O 3 ‐Y 2 O 3 Additives
Author(s) -
Lee Seung Kun,
Kim Chong Hee
Publication year - 1994
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1994.tb09771.x
Subject(s) - materials science , microstructure , fracture toughness , sintering , equiaxed crystals , composite material , ceramic , grain size , silicon carbide , toughness , grain growth
Dense Sic ceramics were obtained by pressureless sintering of β‐Sic and α‐Sic powders as starting materials using Al 2 O 3 ‐Y 2 O 3 additives. The resulting microstructure depended highly on the polytypes of the starting SiC powders. The microstructure of SiC obtained from α‐SiC powder was composed of equiaxed grains, whereas SiC obtained from α‐SiC powder was composed of a platelike grain structure resulting from the grain growth associated with the β→α phase transformation of SiC during sintering. The fracture toughness for the sintered SiC using α‐SiC powder increased slightly from 4.4 to 5.7 MPa.m 1/2 with holding time, that is, increased grain size. In the case of the sintered SiC using β‐SiC powder, fracture toughness increased significantly from 4.5 to 8.3 MPa.m 1/2 with holding time. This improved fracture toughness was attributed to crack bridging and crack deflection by the platelike grains.