The anisotropy of fatigue crack nucleation in an AA7075 T651 Al alloy plate

Yan Jin, Pei Cai, Wei Wen, Hiromi Nagaumi, Bin Xu, Yuanbin Zhang, Tongguang Zhai

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Four-point bend fatigue tests were conducted on the L-T (Rolling-Transverse), L-S (Rolling-Short transverse) and T-S planes of an AA7075 T651 alloy plate, respectively, at room temperature, 20Hz, R=0.1, in air. The populations of crack initiation sites (i.e., fatigue weak-links), measured on these surfaces, were found to be a Weibull-type function of the applied maximum cyclic stress, from which fatigue weak-link density and strength distribution could be determined. The alloy showed a profound anisotropy of fatigue weak-links with the weak-link density being 11mm-2, 15mm-2 and 4mm-2 on the L-T, L-S and T-S planes, respectively. The fact that cracks were predominantly initiated at Fe-containing particles on the L-T and L-S planes, but only at Si-bearing particles on the T-S plane, profoundly demonstrated that the pre-fractured Fe-containing particles were responsible for crack initiation on the L-T and L-S planes, since the pre-fracture of these particles due to extensive deformation in the L direction during the prior rolling operation could only promote crack initiation when the sample was cyclic stressed in the L direction on both the L-T and L-S planes. The fatigue strengths of the L-T, L-S and T-S planes were measured to be 243.6, 273.0 and 280.6MPa, respectively. The difference in grain structure and particle between these planes was responsible for the anisotropy of fatigue strength on these planes.

Original languageEnglish
Pages (from-to)7-15
Number of pages9
JournalMaterials Science and Engineering: A
Volume622
DOIs
StatePublished - Jan 2 2015

Bibliographical note

Publisher Copyright:
© 2014 Elsevier B.V.

Keywords

  • AA7075 Al alloys
  • Anisotropy
  • Constituent particle
  • Fatigue crack nucleation
  • Strength distribution of fatigue weak link
  • Weak-link density

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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