Elastic constants and thermodynamic properties of Mg-Pr, Mg-Dy, Mg-Y intermetallics with atomistic simulations

The temperature dependence of elastic constants and thermodynamic properties of light rare earth ( RE) Mg-Pr, heavy RE Mg-Dy and Mg-Y intermetallics are studied using the modified analytic embedded atom method. The present calculations are generally in agreement with the experimental data and other theoretical results. The bulk moduli of Mg-Pr alloys are smaller than that of Mg-Dy and Mg-Y alloys, which explains why the mechanical properties of Mg-based alloys can be further improved by the addition of heavy RE metals experimentally. Furthermore, heat capacity, vibrational free energy and vibrational entropy of Mg-Pr, Mg-Dy and Mg-Y alloys are calculated in the harmonic approximation, using the vibrational density of states (VDOS) obtained from Born-von Karman theory. The partial VDOS indicates that the VDOS originates from RE atoms at low frequency and from Mg atoms at high frequency and the contribution of RE atoms is dominant in frequency since they are heavier than Mg atoms.