Papers by Author: Baek Seok Seong

Abstract: Deformation behavior of high Mn TWIP (twinning induced plasticity) steels was observed using neutron diffraction. Two kinds of specimens were prepared; 0 and 2 wt% of Al TWIP steels. The lattice strains and peak widths of hkl grains were measured under tensile loading. The results provide an insight into the influence of the Al contents on the deformation behavior associated with the microstructure changes in TWIP steels.

Abstract: In this paper properties of the dedicated neutron strain/stress diffractometer installed at the beam port ST-1 of HANARO reactor in KAERI which has been optimized at a small monochromator take-off angle, are described. Thanks to the employment of the horizontally focusing bent perfect crystal monochromator and the optimization procedure good resolution can be achieved and namely, the luminosity of the instrument can be considerably increased which permits us to enlarge the range of the material depth for residual strain/stress mapping. Moreover, new alternative of the diffractometer permits also to investigate some kinetic processes in polycrystalline materials running within few seconds.

Abstract: The irradiation induced defects of irradiated reactor pressure vessel(RPV) steel were investigated by a small angle neutron scattering. The degradation of the mechanical properties of RPV steels during an irradiation in a nuclear power plant is closely related to the irradiation induced defects. The size of these defects is known to be a few nanometers, and the small angle neutron scattering technique is regarded as the best non destructive technique to characterize the nano sized inhomogeneities in bulk samples. The RPV steel was irradiated in the HANARO reactor in KAERI. The small angle neutron scattering experiments were performed at SANS instrument in the HANARO reactor. Both unirradiated and irradiated RPV steels were measured and the SANS data of both steels were compared. The nano sized irradiation induced defects were quantitatively analyzed by SANS. The type of defects was also analyzed based on the SANS results, and the effect of the chemical composition of the RPV steel on the irradiation induced defects was discussed.