β型粉末を原料とする窒化ケイ素焼結体の疲労挙動

概要

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Beta(β)-Si_3N_4 powder containing 1 mol% equimolar Y_2O_3-Nd_2O_3 was gas-pressure-sintered under three combined conditions of temperature, N_2 gas pressure and time. Cyclic fatigue testing of these materials was performed using smooth specimens in ambient air. The fatigue crack growth diagram (K_<I max>-da/dN diagram) was calculated from the fatigue lifetime distribution data by using the statistical method proposed by Fett and Munz. These materials had a microstructure of "in-situ composites" as a result of exaggerated grain growth of some β-Si_3N_4 grains during firing, and showed high fracture toughness. The crack growth rates of the materials were retarded by high fracture toughness. The threshold K_<I max> value of crack growth was recognized in crack growth rate diagrams of these materials. It was deduced that the characteristic fatigue behavior of Si_3N_4 materials prepared from β-phase powder was due to high fracture toughness caused by in-situ composite microstructure.
社団法人日本セラミックス協会の論文
1995-07-01