SiC粒子分散Al_2O_3複合材料における安定き裂成長

概要

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The stable crack growth in Al_2O_3 monolithic and Al_2O_3 matrix composites dispersed with 10-30 vol% SiC particles is examined in strength tests in both air and vacuum using Knoop-indented specimes. The crack growth exponent n, 33 for the Al_2O_3, increases with the volume fraction of SiC particles to 88 for the 30 vol% SiC composite. The increase of n-value with the additon of SiC particles is concluded to result from the increased tendency of transgranular fracture. Due to the thermal expansion mismatch between SiC particles and Al_2O_3 matrix, the residual tensile stress in the matrix is generated in the circumferential direction around the particles, resulting in the particles which attract the crack. The residual stress-induced deviation of the crack bath within the polycrystalline Al_2O_3 matrix increases the percentage of transgranular fracture and the n-value. The relation between the n-value and the R-curve is also discussed qualitatively. When the Knoop-indented specimen is broken under vacuum, a stable crack growth region is found on the fracture surface for the Al_2O_3-SiC composites, but not for the Al_2O_3 monolithic. It is expected that the n-value has a strong correlation to the rising R-curve behavior.
社団法人日本セラミックス協会の論文
1996-10-01