Distinct fatigue limit of a 6XXX series aluminum alloy in relation to crack tip strain-aging

Yoshimasa Takahashi, Ryosuke Kuriki, Jun Kurihara, Tomoyuki Kozawa, Takahiro Shikama, Hiroshi Noguchi

Research output: Contribution to journalArticle

Abstract

In this study, a conventional precipitation-hardened A6061-T6 alloy (base alloy) and a modified alloy containing excess solute magnesium (Mg) compared to the base alloy were compared in terms of high-cycle fatigue property. Particular attention was paid to the emergence of a distinct knee point on the fatigue life diagram together with a time-dependent strengthening (coaxing) effect in the modified alloy under various test conditions. An attempt using specimens with different defect size successfully revealed that a distinct knee, which was absent in the base alloy, was attributed to the threshold against small crack growth. The clear coaxing effect in the modified alloy was also explicitly confirmed in terms of the high ΔK value achieved by the arrested cracks regardless of the defect size. The comparative tests conducted under different environments and temperature conditions further confirmed that the crack tip strengthening, essentially caused by the strain-aging capability endowed to the modified alloy, operated most prominently in the ambient air at room temperature. Such results were rationally interpreted by incorporating a competitive interaction of solute Mg and hydrogen (H) with dislocations at the crack tip.

Original languageEnglish
Article number139378
JournalMaterials Science and Engineering A
Volume785
DOIs
Publication statusPublished - May 21 2020

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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