J. Japan Inst. Metals, Vol. 74, No. 1 (2010),
pp. 24-29

Stress Intensity Factor and Crack Propagation Behavior of Thin α-Alumina

Hajime Matsuo¹, Yusuke Kaieda¹, Nobuhiro Kojima¹, Ken-ichi Ikeda², Satoshi Hata² and Hideharu Nakashima²

Abstract:

This paper reports the mechanical property and crack propagation behavior of thin ceramics. A method to evaluate the stress intensity factor, K_I, of thin ceramics was proposed. Dependence of K_I values on the average grain size, d, of thin α-alumina were measured by the method. K_I values of thin α-alumina decreased with increasing d values from 4.3 μm to 15.2 μm, while the K_I values were almost constant for 15.2 μm ≤ d ≤ 63.0 μm. The trend of K_I values agreed with the dependence of fracture toughness, K_c, of bulk α-alumina. The thin α-alumina specimens after crack propagation were investigated by scanning electron microscopic electron back-scattered diffraction (SEM/EBSD) analysis. Branched cracks were hardly observed, regardless of grain size. The result indicates that the toughing mechanism do not occur in the thin α-alumina. Dependence of the transgranular fracture rate, F, and the crack deflection rate, D, on d were measured from the orientation distribution maps. However, the F values and the D values were independent of d and approximately constant. The F values and D values depend on d in bulk α-alumina. It indicates that the crack propagation behavior is varied by thinning α-alumina.

(Received 2009/7/14)

Keywords:

thin ceramics, polycrystalline alumina, stress intensity factor, transgranular fracture rate, crack deflection rate

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