Effects of Alloying Atoms on Antiphase Boundary Energy and Yield Stress Anomaly of L12 Intermetallics: First-Principles Study

The antiphase boundary energies of {111} and {010} planes in L1 2 intermetallics (Ni 3 Ge, Ni 3 Si, Al 3 Sc, Ni 3 Al, Ni 3 Ga and Al 3 Ti) under different pressure are presented using first-principle methods. The yield stress anomaly is predicted by the energy criterion p-factor based on the anisotropy of antiphase boundary energies and elasticity. These L1 2 intermetallics exhibit anomalous yield stress behavior except Al 3 Sc. It is found that pressure cannot introduce the transition between anomalous and normal behavior. In order to investigate the transition, Al 3 Sc, Ni 3 Si and Ni 3 Ge with substituting atoms are investigated in detail due to p-factors of them are close to the critical value pc=√3 . Al 3 Sc can change to anomalous when Sc atoms in {010} planes are substituted by Ti with plane concentration 25%. When Li substitutes Al in {111} planes, anomalous Al 3 Sc will change to normal. Ni 3 Si and Ni 3 Ge can exhibit normal yield stress behavior when Ge and Si in {111} planes are substituted by alloying atoms with plane concentrations 12.5% and 25%. When Ga and Al substitute in {010} planes, normal Ni 3 Si and Ni 3 Ge will revert to anomalous behavior. Therefore, transparent transition between normal and anomalous yield stress behavior in L1 2 intermetallics can be introduced by alloying atoms.