Strength-Toughness Relations in Sintered and Isostatically Hot-Pressed ZrO2-Toughened Al2O3 |
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Authors: | SABURO HORI,MASAHIRO YOSHIMURA,SHIGEYUKI S MIYA |
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Affiliation: | Kureha Chemical Industry Co., Ltd., 16 Ochiai, Nishikimachi, Iwaki-shi, Fukushirna 974, Japan;Research Laboratory of Engineering Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-Ku, Yokohama 227, Japan |
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Abstract: | The fracture toughness of fine-grained undoped ZrO2-toughened Al2O3 (ZTA) was essentially unchanged by postsintering hot isostatic pressing and increased monotonically with ZrO2 additions up to 25 wt%. The strength of ZTA with 5 to 15 wt% tetragonal ZrO2, which depended monotonically on the amount of ZrO2 present before hot isostatic pressing, was increased by pressing but became almost constant between 5 and 15 wt% ZrO2 addition. The strength appeared to be controlled by pores before pressing and by surface flaws after pressing; the size of flaws after pressing increased with ZrO2 content. The strength of ZTA containing mostly monoclinic ZrO2 (20 to 25 wt%) remained almost constant despite the noticeable density increase upon hot isostatic pressing because the strength was controlled by preexisting microcracks whose extent did not change on postsintering pressing. These strength-toughness relations in sintered and isostatically hot-pressed ZTA are explained on the basis of R -curve behavior. The importance of the contribution of microcracks to the toughness of ZTA is emphasized. |
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