High temperature creep properties of a silicon carbide reinforced alumina.

摘要

Ceramic matrix composites have potential applications as high temperature structural materials. Therefore, the creep properties and the creep mechanisms of the composites become important.; SiC whiskers or particulates reinforced alumina composite, as well as monolithic alumina, were investigated in the present work. These composites were fabricated using a colloidal dispersion processing. SiC whiskers were ball milled and the whiskers with different aspect ratios were incorporated into the {dollar}rm Alsb2Osb3{dollar} matrix.; Four-point bending creep tests were used to study the creep rates of the monolithic {dollar}rm Alsb2Osb3{dollar} and {dollar}rm Alsb2Osb3{dollar} composites. {dollar}rm Alsb2Osb3{dollar} composites reinforced with long whiskers had best creep resistance. The creep rates of monolithic {dollar}rm Alsb2Osb3{dollar} were about three orders of magnitude higher than that of whisker reinforced {dollar}rm Alsb2Osb3{dollar} composites having large whisker aspect ratio, whereas the strain rates of particulate composites were between that of monolithic {dollar}rm Alsb2Osb3{dollar} and the whisker reinforced {dollar}rm Alsb2Osb3.{dollar} 15 vol% of SiC whiskers or particles reinforced alumina exhibited a significant anelastic recovery when the load was removed whereas monolithic {dollar}rm Alsb2Osb3{dollar} and 5 vol% whiskers or particles reinforced {dollar}rm Alsb2Osb3{dollar} showed no evidence of any an elastic response.; Scanning electron microscopy observations showed that the SiC whiskers or particles are reasonably homogeneously distributed in the matrix whereas transmission electron microscopy examination indicated that SiC whisker networks were formed in whisker-reinforced alumina. No or little glass phase and cavitation was observed in the composites.; A network creep model was developed to explain the creep properties and anelastic creep recoveries of alumina and alumina composites. The SiC whisker or particle networks formed during the materials processing is the origin of the creep rate reduction and anelastic response of the composites. A Maxwell unit in series with a Voigt unit is used to explain the test results of these materials.