Thermodynamically analyzing the formation of Mg₁₂Nd and Mg₄₁Nd₅ in Mg-Nd system under a static magnetic field

Influence of a static 1 T magnetic field on the phase formation and solidified microstructure of Mg-24 wt%Nd alloy at the cooling rates of 6 °C/min and 14 °C/min is studied. Metastable Mg₁₂Nd appears at 14 °C/min and 0 T, while the equilibrium phase Mg₄₁Nd₅ is obtained at the same cooling rate and 1 T. The magnetic field induces the orientation of α-Mg dendrites and leads to the increase of compression strength of alloy (from 153 ± 3.6 to 167 ± 4.4 MPa). The contribution of magnetic field on Gibbs free energy is evaluated for the two phases. Combining with the CALPHAD method, transient nucleation theory and differential scanning calorimetry, the critical undercooling ΔT_c for Mg₁₂Nd and Mg₄₁Nd₅ is analyzed to understand the promotion effect of magnetic field on equilibrium Mg₄₁Nd₅. The ΔT_c of Mg₁₂Nd phase increases under 1 T magnetic field which is greater than that of Mg₄₁Nd₅ (11 °C) at the cooling rate of 14 °C/min.