α-アルミナ単結晶と多結晶のK_I-ν特性について(<小特集>セラミック材料小特集)

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Although the relation between stress intensity factor (K_I) and crack velocity (v) in polycrystalline materials is to be affected by their microstructures such as grain size, porosity, grain boundary and so on, the dependence of subcritical crack growth on microstructures has rarely been investigated. Therefore, in this study, the K_I-v relations for single- and poly-crystalline α-alumina were examined in order to obtain the information about such dependence and to study the stress corrosion mechanism in α-alumina. The specimens with a Chevron notch were fractured by the 4-points bending technique. The tests were carried out under a constant crosshead speed of 0.005mm/min. in air (20℃, 67%rh) and distilled water. The K_I-v relations were obtained by the compliance analysis of load-deflection curves of stable fracture. Also the effective fracture energy (γ_<eff>) was measured by using the work-of-fracture technique. T^2 in air, which were larger than that of single crystal (3.50 J/m^2). The positions of the curves in K_I-v diagram for three materials corresponded to the magnitude of γ_<eff>. The difference in γ_<eff> between two polycrystalline bodies was explained on the basis of grain size. The n-values in u=AK^n_I measured in air and distilled water were nearly equal, and they were 65, 50, and 27 for single-, large grain and small grain poly-crystalline bodies. respectively. This difference may be attributable to the purity of alumina in the bodies. Stress corrosion was hardly observed in single crystal. For the polycrystalline bodies, the stress corrosion resistance was better in a higher purity alumina body. Consequently, it seems that the stress corrosion resistance of polycrystalline bodies depends largely on that of glassy phases in grainboundaries.
社団法人日本材料学会の論文
1983-11-15

α-アルミナ単結晶と多結晶のK_I-ν特性について(<小特集>セラミック材料小特集)

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