Influence of rare-earth addition on the long-period stacking ordered phase in cast Mg-Y-Zn alloys

The microstructure and thermal stability of the Mg97Y2Zn1 (at.%) alloy, modified with the addition of 0.5 at.% of gadolinium or neodymium, have been examined by synchrotron radiation diffraction during in situ differential scanning calorimetry. The microstructure of the three alloys consists of magnesium dendrites with the Long Period Stacking Ordered (LPSO) phase at interdendritic regions. Rare-earth atoms substitute yttrium atoms in the LPSO phase, promoting the formation of the 14H structure. Lattice parameters of the LPSO do not change significantly with the rare-earth addition. However, they reduce the melting point of the LPSO phase, especially in the case of neodymium addition.