Generalized planner fault energies, twinning and ductility of L12 type Al3Sc and Al3Mg

The generalized planner fault energy, twinnability, and ductility of both Al3Sc and Al3Mg are studied by first-principles calculations. The results show that a three-layer thick twin may be described as the smallest twin nucleus for both L1(2) intermetallic compounds Al3Sc and Al3Mg. Because the unstable stacking fault energy (SFE) gamma(us) and unstable twin SFE gamma(yt) of both materials are relatively high, their twin nucleation is very difficult. Meanwhile, both intermetallic compounds exhibit brittle feature because of the low surface energy and high gamma(us). The electronic structure during slipping demonstrates 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 fcc crystal. (C) 2010 Elsevier Masson SAS. All rights reserved.