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Influence of Microstructure on Crack Tip Toughness of α-Sialon Ceramics
C.T. Bodur1, M. Thiele2, M. Herrmann2
1 Istanbul Technical University, Department of Mechanical Engineering, Gümüssuyu 34437 Istanbul, Turkey
2 Fraunhofer Institute for Ceramics Technologies and Systems, Winterbergstrasse 28, 01277, Dresden, Germany
received November 15, 2011, received in revised form April 3, 2012, accepted April 29, 2012
Vol. 3, No. 3, Pages 105-110 DOI: 10.4416/JCST2012-00010
Abstract
For two different α-Sialon ceramics, one with a stoichiometric composition and the other one with an extra amount of yttria, the fracture toughness (SEVNB) and the crack opening displacements (COD) in the crack tip (CT) region were measured. The fracture toughness values were 3.0 MPa√m for the material without excess Y2O3 and 4.5 MPa√m for the material with a residual grain boundary phase. In contrast, the crack tip toughness of α-Sialon with the stoichiometric composition was 1.35 – 1.68 MPa√m and 0.95 – 1.01 MPa√m for the α-Sialon with an excess amount of yttria. Crack behavior in α-Sialon with an excess amount of yttria is both intergranular and transgranular owing to the formation of large elongated grains, and mainly intergranular in α-Sialon with stoichiometric composition. The different crack behavior and the resulting crack tip toughness are the result of the different chemistry and changed microstructure of the materials.
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Keywords
Sialon, microstructure-final, toughness and toughening, mechanical properties, crack tip toughness
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