Atomistic calculations of surface and interfacial energies of Mg17Al12–Mg system

It is well known that precipitation hardening in magnesium (Mg) alloys is far less effective than in aluminum alloys. Thus, it is important to understand the surface and interfacial structure and energetics between precipitates and matrix. In upscale modeling of magnesium alloys, these energy data are of great significance. In this work, we calculated the surface and interfacial energies of Mg17Al12–Mg system by carefully selecting the surface or interface termination, using atomistic simulations. The results show that, the higher fraction of Mg atoms on the surface, the lower the surface energy of Mg17Al12. The interfacial energy of Mg/Mg17Al12 was calculated in which the Burgers orientation relationship (OR) was satisfied. It was found that the (011)P|(0002)Mg interface has the lowest interfacial energy (248 mJ/m2). Because the Burgers OR breaks when {101¯2} twin occurs, which reorients the matrix, the interfacial energy for Mg17Al12 and a {101¯2} twin was also calculated. The results show that after twinning, the lowest interfacial energy increases by 244 mJ/m2, and the interface becomes highly incoherent due to the change in orientation relationship between Mg17Al12 and the matrix.