The generalized planar fault energy, twinnability, and ductility of both Al3Sc and Al3Mg were studied by first-principles calculations. The results showed that a three-layer thick twin may be described as the smallest twin nucleus for both L12 intermetallic compounds Al3Sc and Al3Mg. Because the unstable stacking fault energy, γus, and unstable twin stacking fault energy γut of both materials were relatively high, their twin nucleation was very difficult. Meanwhile, both intermetallic compounds exhibited brittle feature because of the low surface energy and high γus. The electronic structure during slipping demonstrated that the electronic density of states and charge density distribution of both intermetallic compounds vary dramatically at the fault layers, and alters the valence–bonding hybridization, so dislocation nucleation would be difficult owing to such large variation of electronic structure deviated from the initial perfect face-centered cubic crystal.

Generalized Planar Fault Energies, Twinning and Ductility of L12 Type Al3Sc and Al3Mg. J.Wu, L.Wen, B.Y.Tang, L.M.Peng, W.J.Ding: Solid State Sciences, 2011, 13[1], 120-5