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 (Ni3Ge, Ni3Si, Al3Sc, Ni3Al, Ni3Ga and Al3Ti) 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 Al3Sc. It is found that pressure cannot introduce the transition between anomalous and normal behavior. In order to investigate the transition, Al3Sc, Ni3Si and Ni3Ge with substituting atoms are investigated in detail due to p-factors of them are close to the critical value p(c) = root 3. Al3Sc 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 Al3Sc will change to normal. Ni3Si and Ni3Ge 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 Ni3Si and Ni3Ge 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.