Effect of solute atoms on grain boundary stability of nanocrystalline Ni–Co alloy

In this contribution, molecular dynamics method is used to accurately add quantitative Co atoms in the grain boundary (GB) region of nano-polycrystalline Ni to study the effect of solute atoms on the GB and the deformation mechanism of the material. It was found that adding an appropriate amount of Co atoms at the GBs can improve the tensile strength of the material to a certain extent through solid solution strengthening. However, excessive introduction of solute atom will increase the activity of GB atoms, destroy the stability of GBs, and accelerate the appearance of material yielding. At the same time, the Co atoms at the GB gradually detached from the GB region and diffused into the grains. In addition, the dislocations are distributed in a grid at the GBs, and with the increase in strain, the number and length of dislocations gradually increase, forming a large number of entanglements. Moreover, the Shockley dislocation interacts with other dislocations to form a more stable dislocation structure by hindering the generation and movement of other dislocations, which greatly enhances the strength of the system.