Unveiling dislocation characteristics in N i3Al from stacking fault energy and ideal strength: A first-principles study via pure alias shear deformation

Nickel aluminide (Ni3Al) is an important material for a number of applications, especially when used as a strengthening constituent in high-temperature Ni-based superalloys. Despite this, there is minimal information on its mechanical properties such as strength, plasticity, creep, fatigue, and fracture. In the present work, a first-principles based pure alias shear deformation has been applied to shed light on dislocation characteristics in Ni3Al using the predicted stacking fault energy (i.e., the γ surface) and ideal shear strength (τIS). Results include direct evidence for the splitting of a 1/2[110] dislocation into two Shockley partials on the {111} plane, which is further supported by the equivalence of the complex stacking fault (CSF) energy γCSF and the antiphase boundary (APB) energy γAPB111. Estimates of the Peierls stresses using τIS and elastic properties suggest the prevalence of edge dislocations in Ni and screw dislocations in Ni3Al, agreeing with experimental observations regarding the dominance of edge dislocations in the first stage of crystal deformation in fcc metals and the yield-strength anomaly related to screw dislocations in Ni3Al. The present calculations further point out that the CSF and APB111 are easily formed by shear due to the low-energy barriers, although the lowest planar energies are for the superlattice intrinsic stacking fault and the APB001. Through the case of Ni3Al, the present work demonstrates that the pure alias shear methodology is not only computationally efficient but also provides valuable insight into the nature of shear-related properties.