在本實驗中，對含不同濃度鈮酸釔之3Y-氧化鋯材料進行單軸向高壓應力循環負載和潛變實驗，研究此材料在高壓應力狀態下各種韌化機制發生之時機與強度。添加鈮酸釔的濃度分別為2mol%與4mol%，而實驗試片為骨頭狀外型且可以承受平面應力負載之薄片。
經過數次的循環負載後，將所得的實驗數據繪製成圖表，觀察應力-軸向應變曲線迴路位置之變動情形，並分析討論即時楊氏模數、即時體積模數和即時波松比值之變化。結果顯示試片在承受壓應力負載過程時，當負載達到某個高壓應力階段（添加2mol%鈮酸釔之3Y-氧化鋯試片負載至-1625MPa，添加4mol%鈮酸釔之3Y-氧化鋯試片負載至-1629MPa），會有大量的非彈性變形行為發生，以相變化為主要的韌化機制，而適當地增加鈮酸釔濃度可以促進應力誘發相變化的發生。另ㄧ方面，試片在高壓應力負載後進行潛變，相變化會持續發生。而在高壓應力下潛變時所誘發出來的相變化，也會在0MPa潛變時逆轉回去。

Specimens of 3Y-zirconia tetragonal polycrystals, doped with various concentrations of YNbO4, were subjected to high compressive stress cyclic loading. Creeping at the upper and lower ends of some cyclic loading was also performed. The specimens are in the form of a thin plate to ensure a plane stress loading in the central portion where the longitudinal and transverse gages are bonded. The instantaneous Young’s modulus, instantaneous Poisson’s ratio and instantaneous bulk modulus, along with the stress-strain curves and stress-volume dilatation curves, were analyzed to reveal the occurring intensity of various toughening mechanisms, such as domain reorientation and phase transformation, at different stress levels.

An abrupt increase of the fluctuation of the instantaneous Young’s modulus, instantaneous Poisson’s ratio and instantaneous bulk modulus was perceived when the compressive stress reaches some high level, such as –1625 and –1629 MPas for 2 and 4 mol% specimens, respectively. Before these critical levels, these three instantaneous mechanical properties increase gradually, but stay close to their corresponding elastic values. Intriguingly, in the beginning of loading, these instantaneous mechanical properties also fluctuate in a much more moderate extent than after the critical stress levels. It’s been found that some volume-dilatational phase transformation takes place massively after the critical values, producing substantial inelastic deformation to offset the elastic one. At some stress point, the material exhibits incompressibility with an instantaneous Poisson’s ratio of 0.5. The phase transformation appears to be undone by its reverse transformation during unloading. It’s noteworthy that the phase transformation seems to occur significantly right in the beginning of loading.

1.Green, D. J., Hannink, R. H. J. and Swain, M. V., ”Transformation toughening of ceramics”, Fla: CRC Press(1989).
2.Rodriguez, A. M., Caracoche, M. C., Rivas, P. C., Psquevich, A. F. and Minzer, S. R., ”PAC characterization of nontransformable tetragonal t’ phase in arc-melted zirconia-2.8mol% yttria ceramics”, J.Am. cream.Soc. 84[1]188-92(2001).
3.Cain, M. G. and Lewis, M. H., “Evidence of Ferroelastic in Y-Tetragonal Zirconia Polycrystals”, materials letters, 9[9],309-12 (1990).
4.Foitzik, A., Klenke, M. S. and Ruhle, M., “Ferroelasticity of t’-ZrO2”, Z. Metallkd. 84[6] 397-404 (1993).
5.Quinn, C. and Wusirika, R., “Twinning in YNbO4”, J. Am. Ceram. Soc., 74[2] 431-32 (1991).
6.Rauchs, G., Fett, T., Munz, D. and Oberacker, R.,“Tetragonal to monoclinic phase transformation in CeO2-stabilised zirconia under uniaxial loading”,Journal of the European Ceramic Society.,21, 2229-41(2001).
7.Butler, E. P., “Transformation-toughened ceramics”, Mater. Sci. Tech.1,417-432(1985).
8.Chien, F. R., Ubic, F. J., Prakash, V. A. and Heuer, H., ”Stress-induced martensitic transformation and ferroelastic deformation adjacent microhardness indents in tetragonal zirconia single crystals”,Acta mater.,46[6],2151-2171(1998).
9.Virkar, A. V. and Matsumoto, R. L. k., “Ferroelastic domain switching as a toughening mechanism in tetragonal zirconia”, J.Am.Ceram. Soc., 69[10],C-224-26(1986).
10.Chan, C. J., Lange, F. F. and Ruhle, M., “Ferroelastic domain switching in tetragonal zirconia single crstals microstructural aspects”, J. Am. Ceram. Soc.,74[4],807-13(1991)
11.Kyowa共和電業,“應變規使用說明”,三聯科技股份有限公司。