Dislocations in Deformation Microstructure of Extruded Mg₉₇Y₂Zn₁ Alloy Studied by High-Angle Annular Detector Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM)

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Dislocations in the deformation microstructure of α-Mg and long-period stacking phase (LPS) crystals in an Mg₉₇Y₂Zn₁ alloy extruded at 350°C are studied by high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). Extended a-dislocations in α-Mg crystals are observed as bright line contrasts being parallel to close-packed planes in HAADF-STEM images, showing the segregation of Y and Zn at stacking faults of the extended a-dislocations. On the other hand, a-dislocations in LPS crystals are represented as dark lines in bright fringes of Zn/Y-rich planes periodically arrayed in the LPS structure. Various grain boundaries with slow or sharp bends of close-packed planes are formed by configurations of a series of a-dislocations in the α-Mg and LPS crystals.