Revealing mechanical property-strengthening micro-mechanism of Ni/NiAl-based alloys by molecular dynamics simulation.

In this study, the Ni/NiAl-based alloys were proposed, and their microstructures were established. Uniaxial tension was performed based on the γ' phase precipitates of alloys with different shape ratio by means of molecular dynamics (MD) simulations. We demonstrate that the crystal distortion induced by the transition from FCC to disordered structure can lead to the reduction of tensile strength. Besides, the structure, temperature, and strain rate effects on the mechanical properties were clarified, and the microscale mechanism was revealed. The results indicated that compared with Ni/NiAl structure with a γ' phase precipitate shape ratio of 1:1:1, the tensile strength of the structure with a shape ratio of 1:2:1 is smaller, and the mechanical property-strengthening effect is significantly determined by the structures of the γ' phase precipitates; besides, there is a clear secondary strengthening in the tensile process of Ni/NiAl structure with a γ' phase precipitate shape ratio of 2:1:2 due to the formation of disordered structures. The elastic modulus and tensile strength of the models with different γ' phase precipitates shape ratios all decrease with the increase of temperature, under the conditions of low strain rate; the tensile strength of the alloys decreases with the decrease of strain rate.