Simulation on shear deformation property of nano-polycrystalline Ni-Co alloy with concentration gradient

In concentration gradient (CG) nano-polycrystalline Ni-Co alloy, the deformation mechanism of each region is different with the increase of Co content. It is found that in the Co-free region, grain boundary diffusion and dislocation slip mechanisms are dominant, while in other regions, there is a synergistic effect of solid solution strengthening. Moreover, the formation of new small grains by the migration of GB atoms will assist in the deformation of large grains, and the alloy exhibits gentle and stable stress-strain curve pattern. Meantime, although the dislocation density of each region is different, the dislocation density still changes stably before and after shearing. Compared with the uniform structure, the flow stress fluctuation is small when the CG structure is plastically deformed, which proves that this kind of structure is more stable. Moreover, it is found that at different temperatures, the CG alloy also shows stable dislocation density and coordination of various mechanisms, which ensures the strength stability. It is revealed that the CG structure has important properties that make the material strength more stable. This work demonstrates the excellent properties of CG alloy and has positive guiding significance for the development of low-cost, high-performance materials in terms of theoretical and practical applications.