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High‐Temperature Creep Deformation of Alumina — SiC‐Whisker Composites
Author(s) -
Lin HuaTay,
Becher Paul F.
Publication year - 1991
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.1151-2916.1991.tb07804.x
Subject(s) - whisker , creep , materials science , whiskers , composite material , nucleation , grain boundary sliding , grain boundary , intergranular corrosion , crystallite , amorphous solid , alloy , microstructure , metallurgy , crystallography , chemistry , organic chemistry
The creep resistance at temperatures between 1200° and 1300°C in air of alumina—SiC‐whisker composites was investigated via four‐point flexure to examine (1) the effect of whisker content and (2) the influence of densification additives (i.e., Y 2 O 3 (plus MgO)). The creep resistance of polycrystalline alumina is greatly improved with the addition of ≤ 20 vol% SiC whiskers. The interlocking/pinning of grains by whiskers which limits grain‐boundary sliding contributes to the improvement in creep resistance. However, the creep rates of alumina composites in air increase at whisker contents ≥ 30 vol%. Electron microscopy observations suggested that the degradation in creep resistance for whisker content ≥ 30 vol% originated from (1) the promotion of creep cavitation and subsequent microcrack generation from the higher number density of nucleation sites and (2) more extensive formation of grain‐boundary amorphous phase(s) associated with an observed increased oxidation rate. Along this one, the excellent creep resistance of alumina composites containing 20 vol% SiC whiskers was significantly degraded by the presence of the intergranular amorphous phases introduced by the addition of the Y 2 O 3 densification additive.