Creep of magnesium strengthened with high volume fractions of yttria dispersoids

B. Q. Han, D. C. Dunand*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Creep experiments were performed on dispersion-strengthened-cast magnesium (DSC-Mg), consisting of unalloyed magnesium with 1 μm grain size containing 30 vol.% of 0.33 μm yttria particles. Strain rates were measured for temperatures between 573 and 723 K at compressive stresses between 7 and 125 MPa. DSC-Mg exhibits outstanding creep strength as compared with other magnesium materials, but is less creep resistant than comparable DSC-Al and other dispersion-strengthened aluminum materials. Two separate creep regimes were observed in DSC-Mg, at low stresses (σ < 30 MPa), both the apparent stress exponent (napp ≈ 2) and the apparent activation energy (Qapp ≈ 48 kJ mol-1) are low, while at high stresses (σ > 34 MPa), these parameters are much higher (napp = 9 - 15 and Qapp = 230-325 kJ mol-1) and increase, respectively, with increasing temperature and stress. The low-stress regime can be explained by an existing model of grain-boundary sliding inhibited by dispersoids at grain-boundaries. The unexpectedly low activation energy (about half the activation energy of grain boundary diffusion in pure magnesium) is interpreted as interfacial diffusion at the Mg/Y2O3 interface. The high-stress regime can be described by dislocation creep with dispersion-strengthening from the interaction of the submicron particles with matrix dislocations. The origin of the threshold stress is discussed in the light of existing dislocation climb, detachment and pile-up models.

Original languageEnglish (US)
Pages (from-to)235-244
Number of pages10
JournalMaterials Science and Engineering A
Volume300
Issue number1-2
DOIs
StatePublished - Feb 28 2001

Keywords

  • Creep
  • Magnesium
  • Metal matrix composites
  • Oxide-dispersion-strengthened materials
  • Threshold stress
  • Yttria

ASJC Scopus subject areas

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

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