Effect of Gradient Nanotwins on Mechanical Properties of Ni-Co Alloy

Gradient nanostructured metals have become one of the research hotspots in the field of materials science due to their excellent mechanical properties and unique deformation behavior. In our contributions, the nanotwin gradient was introduced into the nanocrystalline Ni-Co alloy, and the influence of the gradient structure on the shear properties and microscopic deformation behavior was studied in order to reveal the strengthening mechanism. The gradient nanotwin Ni-Co alloy has elastic deformation and work hardening at the initial shear stage. The stress decreases after reaching the stress limit, and the uniform plastic deformation is maintained at the later stage. The excellent stability of fine twin layer and its effective hindrance to dislocation nucleation and movement can improve the strength of the material. In addition, the yield and work hardening of nanotwin gradient Ni-Co alloy are easy to occur at low temperature, and the stress-strain curve fluctuates obviously. At high temperature, the alloy is prone to plastic deformation, and the strength is reduced macroscopically. The higher the temperature is, the more difficult it is to yield. The results provide a solid theoretical basis for the design of Ni-based alloys. The effect of gradient twin structure on deformation mechanism of cylindrical alloy was studied by molecular dynamics. It is interesting that the grain deformation mechanism changes with the change of nanotwin layer spacing, and the hindrance effect of nanotwin boundary on dislocation expansion is discussed in detail. These findings provide positive and interesting insights into the design of advanced alloys.image (c) 2023 WILEY-VCH GmbH