| 研究実績の概要 |
Hydrogen-induced ductility loss is an important research topic needing to be resolved for ultrahigh strength steel plates. The neutron diffraction was employed to evaluate the initial bulk texture of a high strength steel plate using cubic sample and dog-bone shaped tensile sample, respectively. The consistent texture results confirmed the technical reliability to measure local textures of any fractured dog-bone tensile sample. Moreover, by using the tensile samples marked with initial plate directions, neutron diffraction patterns from the tensile and transversal axes were collected during plastic deformation, and the relative change in integrated intensity of principle diffraction peaks was extracted to evaluate the crystal slips/rotations. The local textures at different parts of steel samples and the relative change in integrated intensity showed the hydrogen charging promotes the crystal slips/rotations to rapidly form the stronger tensile fiber texture, resulting into the early necking fracture of high strength steel plate. The texture and microstructure optimization showed certain favorable effect on improving the resistance to direction susceptibility of steel plate.
In addition, the in-house texture measurement technique using a compact neutron source has also employed to evaluate various steel samples, so the future study about delayed fracture of steel materials may be accelerated through the complementary cooperation among RIKEN accelerator-driven compact neutron source, JRR-3 research reactor neutron facility and J-PARC large proton accelerator neutron facility.
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