Structural and compositional modulation in transformation of LPSO structure in Mg97Zn1Y2 cast alloys

Takanori Kiguchi, Yu Ninomiya, Kensuke Shimmi, Kazuhisa Sato, Toyohiko J. Konno

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


This study investigated modulation of the long period stacking order (LPSO) structure in aged Mg97Zn1Y2 alloys using conventional transmission electron microscopy (TEM) and aberration-corrected high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). The irregular stacking sequence of a fragment of 24R-type LPSO acts as a catalyst for the transformation from 18R- to 14H-type LPSO. The elementary step of the transformation from 18R- to 24R-type takes place by the ledge-pair movement on different (0001)Mg planes with Shockley partial dislocations. Each ledge has a transition region in front of it. The transition regions are HCP-type stacking sequence with lower Zn and Y concentrations than those of the FCC-type enrichment layer. The solute elements migrate easily in the region, where solute elements produce a kind of diffusion field. Therefore, structural modulation occurs by a mechanism resembling diffusionaldisplacive transformation. Local strain analysis using HAADF-STEM images has elucidated that lattice spacing of (0001)Mg in the FCC-type enrichment layer is shorter than that in the HCP-type transition region. These structural and compositional irregularities are an elementary step in the transformation of LPSO in Mg97Zn1Y2 alloys. A diffusionaldisplacive type transformation mechanism in LPSO has been proposed.

Original languageEnglish
Pages (from-to)668-674
Number of pages7
JournalMaterials Transactions
Issue number5
Publication statusPublished - 2013


  • Aging
  • Diffusionaldisplacive transformation
  • Ledge
  • Long-period stacking order (LPSO)
  • Magnesium alloy


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