Effects of intrinsic point defects on antiphase boundary energy of γ'-Ni₃Al from first-principles calculations

The effects of intrinsic point defects including antisites, vacancy as well as alloying solutes Mo, Re, W and Ta on {111} antiphase boundary (APB) energy of γ'-Ni₃Al have been investigated via first-principles calculations. The calculated results show that all the point defects are energetically favorable near APB, while Mo substitutions are relatively unfavorable. Ni_Al antisites reduce APB energy and most Al_Ni antisites enhance it, mainly resulting from decreased/increased amount of Ni–Al bonds and ordering energy near Al_Ni/Ni_Al antisites. Single solutes show positive effects on APB energy except substituting Ni sublattice sites on APB plane. Solutes (So) substituting Al site on APB plane shows higher APB energies and would improve the strength of γ'-Ni₃Al. In contrast with Re, W and Mo show stronger effects on APB energy. ELF analysis shows So-Ni with stronger chemical strength than Al-Ni. Vacancy diminishes the APB energy, especially for Al vacancy on APB plane, whose reduced effect even cannot be offset by alloying solutes. However, the calculations of formation energy show that Al vacancy-alloying solute defects have relatively poor stability. The migration barriers of alloying solute motion toward APB plane mediated by Al vacancy on APB plane are relatively low. The negative effect of Al vacancy on APB energy decrease correspondingly. Besides, low migration barriers partially provide the theoretical evidence for solute segregation to APB.