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

Abstract

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 magnesiumgrains with yttriumand 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 °Cwhich was associated with the development of the 18R-type LPSO-phase in themagnesiumgrains. 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.