The diffusion couples of Mg-RE were investigated by scanning electron microscopy（SEM）and electro-probe microanalyzer（EPMA）in order to understand the diffusion behaviors of rare earth elements such as Y、Gd、Nd.The results show that with holding for a long time at a given temperature

there exists a obvious diffusion layer at the contact interfaces of the Mg-Y

Gd

Nd diffusion couples and the solubility of the solute is decreased along the direction of diffusion.The diffusion constants and activation energy of diffusion of Y、Gd、Nd reach 4.0、6.2、31.3×10-9 m2/s and 76.592、76.073、83.556kJ· mol-1

respectively.The diffusion coefficients are increased with increasing in the temperature.At a certain temperature

the diffusion coefficient of the three elements is followed as:DY <DNd <DGd.