Effect of additive elements on plastic deformation: a three-dimensional discrete dislocation dynamics study

Additive elements change plastic deformation in complicated manners, which may directly affect dislocation activities or indirectly affect plasticity associated microstructure. Clarifying such a complexity is still a challenge as it is not easy to decouple various effect mechanisms, especially in experiments. Previous investigations mainly focused on the indirect effect of additive elements on plasticity associated microstructure. In the present work, we try to clarify the direct effect of additive elements on dislocation activities by three-dimensional discrete dislocation dynamics, using the case of Ni-based single crystal superalloys with additive elements Ru, Cr, and Mo. The three additive elements are chosen because they are crucial for the mechanical properties of Ni-based single crystal superalloys. Moreover, their excess volumes are distinct and hence can be representative additive elements. The results show that both the excess volume and concentration of additive elements contribute to the strengthening of single crystal Ni-based superalloys. The strengthening effect enhances as the excess volume increases and the concentration increases, regardless of the loading conditions. Competition mechanisms of additive elements which cause different mechanical features under different loading conditions are also analyzed.