3D-EBSD法と電子顕微鏡画像を併用したクリープボイドと結晶粒界の三次元幾何形状の計測

概要

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With combining 3D-EBSD method and SEM images, authors have firstly observed three-dimensional shape of creep voids and geometrical relationship with grain boundaries. The method is applied to a 1Cr-1Mo-0.25V turbine rotor steel after creep rupture test (580℃,180MPa). Also, interrupted creep specimens are prepared to observe the progress of void growth. Forty sections with 0.5μm interval and 100μm×100μm area are measured by mechanical polishing in order to reconstruct three-dimensional shapes. In the result, four types of creep void are observed. One is sphere type whose radius is about 1μm. It is observed in the specimen whose creep life fraction is 25%. In the specimens with 50% and 75% creep damage, prolate and oblate spheroids whose radius is around 2.5μm are observed. Finally, connected voids are occupied in ruptured specimen. As the creep damage is progressed, not only void growth but also void nucleation is observed. Especially, on prior austenite grain boundary which is three-dimensionally perpendicular to stress, creep voids are nucleated and grown in concentrated manner. However, such nucleated small voids do not affect the volume fraction of creep void.
2010-12-25