In situ monitoring of dislocation, twinning, and detwinning modes in an extruded magnesium alloy under cyclic loading conditions

Di Xie, Zongyang Lyu, Yuan Li, Peter K. Liaw, Huck Beng Chew, Yang Ren, Yan Chen, Ke An, Yanfei Gao

Research output: Contribution to journalArticlepeer-review

Abstract

This work investigates the microscopic deformation mechanisms of an extruded, precipitation-strengthened AZ80 magnesium (Mg) alloy subjected to strain-controlled low-cycle fatigue using in situ neutron diffraction measurements. Results demonstrate that the plastic deformation during cyclic loading is dominated by the alternating {10.2} extension twinning and detwinning mechanisms. The observed deformation mode is strongly texture and precipitate dependent. For the initial texture, the tested material has two major texture components which result in the occurrence of extension twinning during both compression and reverse tension in the first two cycles. The prolonged detwinning process in the following cycles is proposed to relieve the shear stress field of {00.2} grains, leading to the disappearance of twinning. The precipitation strengthening results in an increase of the critical resolved shear stress (CRSS) by ~33 MPa for the extension twinning in this AZ80 alloy. The synergistic effects of the initial texture, precipitation strengthening, and load sharing of various grain families and phases contribute to the complicated evolution of dominant deformation mechanisms, among which elevated dislocation activities are believed to be responsible for the relatively poor low-cycle-fatigue lifetime when compared to other Mg alloys.

Original languageEnglish (US)
Article number140860
JournalMaterials Science and Engineering A
Volume806
DOIs
StatePublished - Mar 4 2021

Keywords

  • Deformation mode transitions
  • In situ neutron diffraction
  • Low cycle fatigue
  • Magnesium alloy

ASJC Scopus subject areas

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

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