Microstructures of long-period stacking ordered phase of Mg-Zn-Y alloy

The microstructures of α-Mg, long-period stacking ordered (LPSO) phases, and kink bands in a Mg-Y-Zn alloy were observed by transmission electron microscopy (TEM). The results showed that extruded Mg₉₇Zn ₁Y₂ alloy included different kinds of phases: 2H-Mg, 2H-Mg with many stacking faults, 14H and 18R. Kink bands tended to occur in areas where there were many intermetallic compounds. The element distribution of Zn/Y/Mg in the LPSO phase including kink boundaries was also analyzed by scanning TEM energy dispersive X-ray spectroscopy. The results showed that the concentrations of atomic Zn/Y decreased, while the concentration of atomic Mg increased at kink boundaries. This can be understood in terms of the dislocation structure of kink boundaries where extended a-dislocations lying on sequential stacking faults in the LPSO phase cause the annihilation of Zn/Y-rich stacking faults between two partial dislocations.