著者

大熊 学 渡辺 修平 篠部 寛 西山 宣正 竹内 晃久 上杉 健太郎 田中 諭 若井 史博

出版者

一般社団法人 粉体粉末冶金協会

雑誌

粉体および粉末冶金 (ISSN:05328799)

巻号頁・発行日

vol.66, no.12, pp.604-610, 2019-12-15 (Released:2019-12-15)

参考文献数

40

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The characterization of the processing-induced defects is a significant step for developing defect-free processing, which is important to the assurance of the mechanical reliability of brittle ceramics. Recent advances in multiscale X-ray computed tomography which consists of micro-CT and nano-CT enables us to observe the three-dimensional (3D) internal structure non-destructively. Micro-CT reveals the distribution of defects in the entire body of a sample, while nano-CT reveals the shape of the identified defect. This powerful imaging tool was used to reveal the complicated 3D morphology of defects evolved during sintering of alumina. The hierarchical packing structure of granules was the origin of several types of strength-limiting defects, which could not be eliminated due to the differential sintering of heterogeneous microstructures. This imaging technique of internal defects provides a link between the processing and the fracture strength for the development of structural materials.

著者

山田 隆介 戸田 裕之 竹内 晃久 ベーゼル 靖子

出版者

公益社団法人 日本鋳造工学会

雑誌

鋳造工学 (ISSN:13420429)

巻号頁・発行日

vol.89, no.1, pp.10-16, 2017

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<p>  A single-distance phase retrieval technique was applied to the contrast-enhanced phase-sensitive imaging of micro segregation in die-cast aluminum alloy. Contrast between regions with and without micro segregation, spatial resolution and signal-to-noise ratio were evaluated to clearly differentiate micro segregations whose density difference from the matrix aluminum is small, making it difficult to visualize and differentiate them using ordinary absorption-contrast imaging. Since spatial resolution more or less drops during the phase retrieval process, a combination of the high-contrast phase-contrast imaging and the high-resolution absorption-contrast imaging was applied to reveal 3D microstructure/fracture relationship in an in-situ tensile test. Each phase-contrast image was registered with a corresponding absorption-contrast image to examine the positional relationship between the fracture path and micro segregation. A sectioning technique was also applied to identify the source of density difference. The results confirmed that three-dimensionally connected bands of micro segregations provide a preferential path for fracture in the die-cast aluminum alloy investigated. The observations suggest that the control of the 3D spatial distribution of micro segregation bands is of crucial importance for enhancing mechanical properties effectively even if its elimination is physically difficult.</p>