Elevated-temperature 'ultra' fast fracture strength of advanced ceramics: an approach to elevated-temperature 'inert' strength

摘要

The determination of "ultra" fast fracture strengths of five silicon nitride ceramics at elevated temperatures has been made by using constant stress-rate ("dynamic fatigue") testing with a series of "ultra' fast test rates. The test materialsincluded four monolithic and one SiC whisker-reinforced composite silicon nitrides. Of the five test materials, four silicon nitrides exhibited the elevated-temperature strengths that approached their respective room-temperature strengths at an "ultra'fast test rate of 3.3×10{sup}4 MPa/s. This implies that slow crack growth responsible for elevated-temperature failure can be eliminated or minimized by using the "ultra" fast test rate. These on going experimental results have shed light on laying atheoretical and practical foundation on the concept and definition of elevated-temperature "inert" strength behavior of advanced ceramics.