Molecular dynamics simulations of thermodynamics,elastic constants and solid solution strengths for Mg-Gd alloys

The thermal and mechanical properties of Mg-Gd intermetallics MgGd, MgGd₂ and MgGd₃ are studied using a modified analytical embedded atom method. Calculated results agree well with the available experimental data and other theoretical results. The results on the elastic constants suggest that thermal softening behavior is observed as the temperature increases and the bulk moduli of ordered phases are larger than that of elemental Mg above 300 K. The heat capacities of MgGd, Mg₂Gd and Mg₃Gd are 22.91, 23.04 and 23.09 J mol K^-1, respectively, at 300 K. Furthermore, the addition of Gd gives rise to an increase of c/a. With the same content of Gd, the ratio c/a remains unchanged with increasing temperature, whereas this phenomenon does not occur in pure Mg, which indicates that the temperature-independent c/a restrains the occurrence of non-basal slip and twinning. Hence the addition of Gd can enhance the strength of Mg, in good agreement with experimental observation.