Investigation of physical properties and superdislocation characters of Ni3Al under uniaxial tension/compression normal to slip plane

Abstract The {111} superdislocations play a key role in the mechanical behaviors of L12 Ni3Al. Through the combination of density functional theory (DFT) calculations and Peierls-Nabarro (P–N) model, the physical properties of Ni3Al and the characters of superdislocations are systematically investigated under different uniaxial tensile/compressive loads normal to {111} slip planes. The influence of applied loads on ideal stress-strain relation, ideal strength, shear modulus along slip direction, anti-phase boundary (APB) energy, γ surface, splitting width of superdislocation (i.e., APB width), core width of super partial dislocations and Peierls stress is thoroughly discussed. The results show that the effects of uniaxial normal tensile/compressive loads on above properties are remarkable for both nonmagnetic (NM) and ferromagnetic (FM) states. The compressive loads along the direction tend to expand the splitting width of superdislocations and the core width of super partial dislocations, which further induce higher Peierls stress and yield strength of Ni3Al, while the tensile loads lead to opposite effects. In addition, it is found that the stability zone of Ni3Al is in the normal applied strain range of −0.14–0.14 rather than −0.18–0.22 as suggested by previous works. For the case free of applied strain (i.e. e = 0), both the predicted APB width and Peierls stress of the NM state are about 10% percent larger than those of the FM state. Obviously, since the physical properties of Ni3Al and characters of superdislocations are asymmetric under tensile/compressive normal loads, the tension/compression asymmetry of the mechanical behaviors for Ni3Al is inherent.