Precoarsening処理により高強度化したAl_2O_3セラミックスのフラクトグラフィ

概要

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Role of precoarsening treatments in the strengthening mechanism were examined by scanning electron microscopy (SEM) observations on the fracture surface of Al_2O_3 ceramics, which were made by hot-pressing under various sintering conditions. Al_2O_3 polycrystals by general silltering procedure yielded the 4 point bending strength of 400 500 MPa, while the precoarsening treatments increased the strength up to 750 MPa. Since the fracture toughness kept the constant value of 3.5 MPa √<m>regardless of the treatments, it is expected that the reduced flaw size resulted in the enhanced strength. From the observations of the fracture origin, it was found that the precoarsening treatments suppressed the stable growih of a flaw during the bending tests and gave the relatively small flaw size. The increased stability of grain boundary near the flaw is thought to be the reason for the reduced stable growih rate of the fiaw. The decreasing tendency of fracture toughness with decreasing flaw size was not observed due to the small grain size, which causes the crack propagation without the development of process zone.
社団法人日本セラミックス協会の論文
1994-12-01