Abstract

Microstructures of high‐strain‐rate superplastic ceramics, based on the 3mol% yttria stabilized zirconia polycrystals, (3Y)ZrO2, were investigated by transmission electron microscopy (TEM) and analytical electron microscopy (AEM). Two types of ceramics were studied: (3Y)ZrO2‐2mass%CaO‐2mass%TiO2 (Sample I) and (3Y)ZrO2‐2mass%CaO‐6mass%SiO2 (Sample II). Samples were synthesized by the sintering process. Doping CaO, the grain size of the specimen was controlled to keep the size near or less than 300 nm in diameter. While doping TiO2, the boundary gliding process was enhanced during the tensile deformation test at high temperature. Tensile deformation is applied to these samples by an Instron‐type testing machine equipped with an electric furnace. The tensile elongation to failure was 404 and 64% for Samples I and II, respectively. For these two types of ceramics, TEM observations were performed and microstructures were compared between as‐sintered specimens and as‐deformed specimens. In Sample I, grain growth of the zirconia crystals did not occur during the deformation, while in Sample II the grain growth did occur. In the latter, a crystal of zirconium silicate, ZrSiO4, grew in a square shape. Not only the grain growth of zirconia but also the square‐shaped single crystal growth are the reasons for poor superplastic property of Sample II.

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