The study on microscopic mechanical property of polycrystalline with SEM moiré method

The local microscopic deformation of polycrystalline low carbon steel under uniaxial tension is measured through SEM moiré method. In order to produce high frequency gratings, focused ion beam (FIB) milling is used due to its direct writing capability. With gratings of 2000lines/mm, the variations o...

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Bibliographic Details
Published in:Optics and lasers in engineering 2012-12, Vol.50 (12), p.1757-1764
Main Authors: Li, Yanjie, Xie, Huimin, Tang, Minjin, Zhu, Jianguo, Luo, Qiang, Gu, Changzhi
Format: Article
Language:English
Subjects:
Deformation
Diffraction gratings
Grain boundaries
Grain boundary
Grains
Gratings (spectra)
Moire fringes
Random phase shifting
Scanning electron microscopy
SEM moiré
Strain
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Summary:The local microscopic deformation of polycrystalline low carbon steel under uniaxial tension is measured through SEM moiré method. In order to produce high frequency gratings, focused ion beam (FIB) milling is used due to its direct writing capability. With gratings of 2000lines/mm, the variations of SEM moiré fringes with the increase of stress around a triple point of grain boundary and inside a grain are observed respectively and it is found that we can tell whether the specimen has yielded by moiré fringes. With gratings of 5000lines/mm, SEM moiré fringes around five different types of grain boundaries are recorded and analyzed with random phase shifting algorithm. By observing the strain fields around different types of grain boundaries, it is found that the deformation fields around these grain boundaries are inhomogeneous and increase with stress. However, the strain distributions are different, which is probably related with the angle between the loading direction and the grain boundary and the misorientation of two adjacent grains. It is also found that the inhomogeneous strain is caused by slip and the bending direction of moiré fringes is in agreement with the direction of slip band. ► Gratings up to 5000lines/mm on low carbon steel are fabricated with FIB. ► SEM moiré fringes can tell us whether the specimen has yielded. ► SEM moiré fringes are processed with random phase shifting algorithm. ► Strain fields around different grain boundaries are analyzed. ► The inhomogeneous strain is caused by slip.
ISSN:0143-8166
1873-0302
DOI:10.1016/j.optlaseng.2012.07.004