張出し成形した焼戻しマルテンサイト鋼板の水素脆化に及ぼす残留応力の影響

Translated title of the contribution: Effects of residual stress on hydrogen embrittlement of a stretch-formed tempered martensitic steel sheet

Hayato Nishimura, Tomohiko Hojo, Saya Ajito, Yuki Shibayama, Motomichi Koyama, Hiroyuki Saitoh, Ayumi Shiro, Ryo Yasuda, Takahisa Shobu, Eiji Akiyama

Research output: Contribution to journalArticlepeer-review

Abstract

The effects of residual stress on the hydrogen embrittlement behavior of a tempered martensitic steel sheet with 1-GPa-class tensile strength stretch-formed by a hemisphere punch simulating press-formed automotive structural parts were investigated. Cracking on the stretch-formed specimen induced by potentiostatic hydrogen charging was initiated in the foot of the impression of the specimen and propagated to the radial direction both toward the hillside and the plain. The mixture of quasi cleavage and intergranular fractures were observed whole through the fracture surface. Residual stress in the stretch-formed specimens was analyzed by using energy-dispersive X-ray diffraction method utilizing the synchrotron X-ray radiation at SPring-8. In addition, stress and plastic strain distributions in the specimen were analyzed by using Finite Element Method (FEM). These analyses depicted that the high tensile stress in the circumferential direction was in the foot of the impression, corresponding to the direction of the crack growth. The FEM analysis revealed that the high triaxial stress was in the foot suggesting accumulation of hydrogen. It was considered that the preferential crack initiation at the foot was promoted by the high residual stress in the circumferential direction and the hydrogen accumulation due to stress-induced diffusion.

Translated title of the contributionEffects of residual stress on hydrogen embrittlement of a stretch-formed tempered martensitic steel sheet
Original languageJapanese
Pages (from-to)760-768
Number of pages9
JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
Volume107
Issue number9
DOIs
Publication statusPublished - 2021 Sep

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Metals and Alloys
  • Materials Chemistry

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