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

The local microscopic deformation of polycrystalline low carbon steel under uniaxial tension is measured through SEM moire method. In order to produce high frequency gratings, focused ion beam (FIB) milling is used due to its direct writing capability. With gratings of 2000 lines/mm, the variations of SEM moire 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 moire fringes. With gratings of 5000 lines/mm, SEM moire 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 moire fringes is in agreement with the direction of slip band. (C) 2012 Elsevier Ltd. All rights reserved.