  Solute segregation plays an important role in formation of long-period
stacking ordered (LPSO) structure in Mg-M-RE (M: Zn, Ni etc., RE: Y, Gd, etc.)
alloy systems. In this work, the planar segregation in Mg-Al-Gd alloy is
characterized by high angle annular dark field (HAADF) scanning transmission
electron microscopy (STEM) and three-dimensional atom probe (3DAP). It is found
there is no planar fault accompanying the segregation, and the spatial
distribution of segregation may resemble the periodicity of LPSO structure. The
segregation is further quantified by 3DAP, and it mainly enriches with Gd
atoms. The segregation behaviour is rationalized by First-Principles
calculation.
