Atomic-scale investigation of precipitate phases in QE22 Mg alloy

Xiaojun Zhao, Zhiqiao Li, Aiping Zhang, Longlong Hao, Houwen Chen, Jian Nie

Research output: Contribution to journalArticleResearchpeer-review

3 Citations (Scopus)

Abstract

Precipitation-hardenable commercial Mg alloy QE22 (Mg-2.5Ag-2.0Nd-0.7Zr, wt.%) has excellent mechanical properties, but precipitates in this alloy have not been well understood. In this work, precipitate phases γ'', γ, and δ formed during the isothermal ageing process at 150, 200, 250, and 300 °C have been characterized using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy and atomic-scale energy-dispersive X-ray spectroscopy. The morphology, crystal structure, and orientation relationship of these precipitate phases have been determined. Domain boundaries usually exist in a single γ particle, which can be characterized by a separation vector of [11¯01]α. The δ phase forms in situ from its precursor γ phase, consequently leading to the formation of three different variants within a single δ particle. The nucleation of the δ phase is strongly related to the domain boundaries of the γ phase. The formation of the γ phase may be promoted by its precursor γ'' phase. The similarities in atomic structures of the γ'', γ, and δ phases are described and discussed, indicating that transformations between these precipitate phases can be accomplished through the diffusion of added alloying elements.

Original languageEnglish
Pages (from-to)114-127
Number of pages14
JournalJournal of Materials Science and Technology
Volume177
DOIs
Publication statusPublished - 1 Apr 2024

Keywords

  • Electron microscopy
  • Magnesium alloy
  • Phase identification
  • Phase transformation
  • Precipitation

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