Phase Transformation and Mechanical Properties of Reaction Sintered Mullite-Zirconia (Yttria) Composite

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J. Korean Ceram. Soc. > Volume 28(7); 1991 > Article

Journal of the Korean Ceramic Society 1991;28(7): 549.

반응소결된 물라이트-지르코니아(이트리아) 복합체의 상변태와 기계적 성질에 관한 연구

오경영, 장성도¹

동신대학 무기재료공학과
¹한국과학기술연구원

Phase Transformation and Mechanical Properties of Reaction Sintered Mullite-Zirconia (Yttria) Composite

ABSTRACT

Mullite-zirconia (0∼4 mol% yttria) composites were obtained by In-situ sintering of zircon and alumina mixture, and their mechanical properties were studied in conjuction with microstructure observation. Martensitic transformation temperature (Ms) of zirconia dispersed in the mullite matrix decreased with Y2O3 contents and was about 600$^{circ}C$ for ZrO2 containing 4 mol% Y2O3. On cooling of this composites, tetragonal to monoclinic phase transformation induced microcracks at the grain boundary of mullite matrix. The microcracks seemed to absorb the fracture energy in stress field during mechanical tests. Therefore, toughening mechanisms of this composite were considered to nucleation and extension of microcrack, and crack deflection mechanism due to the difference of thermal expansion coefficient between matrix and dispersed phase.