Journal
INTERMETALLICS
Volume 136, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.intermet.2021.107258
Keywords
P-N model; Ni3Al; Superdislocation core structures; Anti-phase boundary energy; Peierls stress; Tension/compression asymmetry
Categories
Funding
- NSFC [11822204, 12072123]
- National Science and Technology Major Project [2017-IV-0003-0040]
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The physical properties of L1(2) Ni3Al and the characteristics of superdislocations are studied under different uniaxial tensile/compressive loads. The applied loads have significant effects on the mechanical behaviors of Ni3Al, showing opposite effects under tension and compression. The tension/compression asymmetry is inherent due to the asymmetric properties and characteristics of superdislocations under normal loads.
The < 110 >{111} superdislocations play a key role in the mechanical behaviors of L1(2) 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, gamma 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 < 111 > 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. epsilon = 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.
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