Abstract
X-ray fluorescence holography was applied to dilute Mg99.2Zn0.2Y0.6 alloy annealed at 520°C for 5 h to obtain atomic images around Zn atom. In spite of the extremely low concentration of the solute-element, clear hologram patterns were obtained. The reconstructed atomic images revealed that the Zn atom in this annealed Mg99.2Zn0.2Y0.6 alloy mainly occupy the hcp Mg site. This finding is consistent with the transmission electron microscope image, where fcc-type stacking faults are hardly observed. These results are in contrast to the previous report that Zn and Y form short-range-ordered solute clusters at the fcc-type stacking fault in Mg–Zn–Y alloy. The effect of heat treatment on the atomic arrangement of solute-elements in this dilute alloy is discussed in relation to the previously reported mechanical properties.
Fig. 5 Atomic images around Zn obtained from XFH measurements on the planes at (a)
z = 0, (b)
z = 2.6 Å, and (c)
z = 5.2 Å. Calculated atomic images of
hcp Mg on the planes at (d)
z = 0, (e)
z = 2.6 Å, and (f)
z = 5.2 Å. Schematic illustrations of these planes are shown in the upper part. Solid circles indicate ideal positions of Mg atoms around Zn at the substitutional site of
hcp Mg structure. Dashed circles in (a) indicate expected positions of intra-cluster Zn atoms in the L1
2-type Zn
6Y
8 cluster. Thin dotted circles in (c) indicate the positions of Mg atoms around Zn located in the
fcc-type stacking fault.
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