Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Evaluation of Fracture Toughness and Fracture Resistance of Sialon at Elevated Temperature
Haruo NAKAMURAHideo KOBAYASHIAtsushi TANAKANagatoshi OKABEHideyuki HIRATA
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1994 Volume 43 Issue 495 Pages 1578-1583

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Abstract

Fracture toughness tests were conducted by using compact specimens of a sialon in the temperature range from room temperature to 1500°C. At elevated temperatures, a fracture initiation and a fracture resistance curve (R-curve) were evaluated by the multiple specimen method.
The fracture toughness, Kc, at unstable fracture by cleavage becomes constant up to 1200°C. Then, it increases up to 1400°C. At 1500°C, the fracture occurred in a stable manner. Above 1200°C, a stable fracture by grain pull out (intergranular fracture) proceeded before unstable fracture. An area percentage of grain pull out increases with temperature rise which brings an increase in slope of R-curve. However, the fracture toghness, Kin, at the initiation of stable crack growth takes maximum at 1400°C and it decreases drastically at 1500°C. So, the viscous flow of glassy phase along grain boundary has a beneficial role on the toughness between 1200°C and 1400°C.

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