Change in mechanical properties of Ti-6Al-4V ELI during fatigue failure process

Toshikazu Akahori, Mitsuo Niinomi, Atsushi Ozeki

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1 Citation (Scopus)


Mechanical properties of biomedical Ti-6Al-4V ELI with equiaxed and Widmanstätten α structures at various fatigued steps were investigated. Fatigue crack initiation characteristics of the same alloy were also investigated in this study. The fatigue crack initiates mainly at the interface between primary a grains in equiaxed α structure while that initiates in the colony along about 45° direction versus stress axis in Widmanstätten α structure. The specimen with Widmanstätten α structure fractures before adequate fatigue hardening because a lot of micro-cracks are easily formed while the specimen with equiaxed α structure fractures after adequate fatigue hardening. The mechanical properties, that is, tensile strength and hardness tend to increase clearly according to the fatigue steps in particular in the low cycle fatigue (LCF) region, while impact toughness and elongation show the reverse trend. The hardness far from the specimen surface is greater than that near the specimen surface at the early stage of LCF. Both hardness is however nearly equal each other at the latter stage of fatigue. It can be understood therefore that the dislocation multiplies near the specimen surface at the early stage of fatigue while at the latter stage of fatigue, the dislocation multiplies also near the center of the specimen. The dislocation multiplication will finally saturates in the whole specimen.

Original languageEnglish
Pages (from-to)140-149
Number of pages10
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Issue number2
Publication statusPublished - 1998


  • Crack initiation
  • Fatigue
  • Mechanical properties
  • Titanium-6aluminum-4vanadium extra low interstitual

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry


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