Formation of an 18R long-period stacking ordered structure in rapidly solidified Mg88Y8Zn4 alloy


The formation of the long-period stacking ordered structure (LPSO) in a Mg88Y8Zn4(at%) ribbon produced by melt spinning was studied using high energy X-ray synchrotron radiation diffraction during in-situ isochronal heating and transmission electron microscopy. The microstructure of the rapidly solidified ribbons is characterised by fine magnesium grains with yttrium and zinc in solid solution and primary 18R LPSO-phase segregated at grain boundaries. Using differential scanning calorimetry, a strong exothermal peak was observed around 300 °C which was associated with the development of the 18R-type LPSO-phase in the magnesium grains. The apparent activation energy calculated using the Kissinger model was 125 KJmol− 1 and it is related to simultaneous diffusion of Y and Zn through magnesium basal plane.
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