Precipitation in Mg-Gd-Y-Zr Alloy: Atomic-scale insights into structures and transformations

This paper reports on a comprehensive investigation, using atomic-scaled Cs corrected high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), of the precipitation in Mg-9.28Gd-2.93Y-0.35Zr, including structures of the precipitates and several structural transformation p...

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Bibliographic Details
Published in:Materials characterization 2016-07, Vol.117, p.76-83
Main Authors: Zheng, Jing-xu, Li, Zhi, Tan, Li-da, Xu, Xue-song, Luo, Rui-chun, Chen, Bin
Format: Article
Language:English
Subjects:
ALLOYS
Atomic structure
Coarsening
DEFECTS
HAADF-STEM
Magnesium base alloys
MATERIALS SCIENCE
Mg alloy
NANOSCIENCE AND NANOTECHNOLOGY
NUCLEATION
Orientation
PHASE TRANSFORMATIONS
Phase transition
Precipitates
PRECIPITATION
Precipitation (chemistry)
SOLID SOLUTIONS
Transformations
TRANSMISSION ELECTRON MICROSCOPY
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Summary:This paper reports on a comprehensive investigation, using atomic-scaled Cs corrected high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), of the precipitation in Mg-9.28Gd-2.93Y-0.35Zr, including structures of the precipitates and several structural transformation processes. The precipitation sequence is identified as: Super saturated solid solution→clusters→nucleation β' (major)/βH (minor)→precipitate β' (major)/βM,βT' (minor)→β1→β(Equilibrium). Under peak-age condition, the strengthening structure is independent defect-free β' with little interaction among each other. Under over-age condition, the β' precipitates start to interact with each other, during which coarsening and orientation transformation of β' precipitates take place. The coarsening and orientation transformation, in which some RE atoms in the precipitates need to change their positions, are achieved by βM and βT' as transitional structures. [Display omitted] •The precipitation in Mg-Gd-Y-Zr is comprehensively investigated by advanced atomic-scale Cs-corrected HAADF-STEM.•Various novel precipitate structures are unraveled.•Four types of interfaces between the precipitates are fully characterized.•The structural transformation processes of the precipitates are revealed.
ISSN:1044-5803
1873-4189
DOI:10.1016/j.matchar.2016.04.015