サイアロンの高温破壊じん性・破壊抵抗の評価

概要

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Fracture toughness tests were conducted by using compact speciments of a sialon in the temperature range from room temperature to 1500℃. At elevated temperatures, a fracture initiation and a fracture resistance curve (R-curve) were evaluated by the multiple specimen method. The fracture toughness, K_c, at unstable fracture by cleavage becomes constant up to 1200℃. Then, it increases up to 1400℃. At 1500℃, the fracture occurred in a stable manner. Above 1200℃, 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 Rcurve. However, the fracture toghness, K_<in>at the initiation of stable crack growth takes maximum at 1400℃ and it decreases drastically at 1500℃. So, the viscous flow of glassy phase along grain boundary has a beneficial role on the toughness between 1200℃ and 1400℃.
社団法人日本材料学会の論文
1994-12-15