Degradation behavior of moduli in extruded pure magnesium during low- to giga-scale cyclic tension fatigue

Hideki Yamagishi, Mikio Fukuhara

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

The mechanical properties of extruded pure magnesium during cyclic tension fatigue in the low- to giga-scale regime at room temperature have been investigated using ultrasonic reflection methods with longitudinal and shear waves. The acoustic velocities and calculated Young's and shear moduli decreased by a large percentage with an increase in the number of cycles in all cycle modes due to growth of grain boundary voids. The eventual degradation of the properties was largest during giga-cycle fatigue, in which the moduli decreased by ∼9%. The elastic behavior depended on the drive stress and the number of cycles rather than on fatigue time. Longitudinal and shear wave propagation characteristics and investigations of a grain boundary before and after fatigue using electron backscatter diffraction based on field-emission scanning electron microscopy and focused ion beam transmission electron microscopy revealed that the largest boundary void gap width was less than several nanometers (almost closed). The Poisson's ratio and bulk modulus were affected notably by the void gap, in which the threshold corresponds to the longitudinal wave amplitude. Other damage phase data were determined using scanning electron microscopy, Vickers hardness, and surface roughness tests under progressive fatigue; these results also indicated slight grain boundary degradation.

Original languageEnglish
Pages (from-to)4759-4767
Number of pages9
JournalActa Materialia
Volume60
Issue number12
DOIs
Publication statusPublished - 2012 Jul 1

Keywords

  • Elastic property
  • Fatigue
  • Grain boundary
  • Magnesium

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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