Synergistic effect of rhenium and tungsten in nickel-based model single crystal superalloys

Understanding the roles and synergistic effects of alloying elements is crucial for designing nickel-based single crystal superalloys. A systematic exploration has been conducted to identify the synergistic effect of rhenium (Re) and tungsten (W) on the mechanical properties and the underlying mechanisms with the experimental characterization and the molecular dynamics (MD) simulations. The experimental results show that the co-addition of Re and W not only has a significant synergistic strengthening effect, but also can improve the work hardening capability. Meanwhile, the co-addition of Re and W results in the majority of Re and more W entering the phase, strengthening the solid solution and forming Re segregation and Re-W segregation. That increases the resistance to dislocation motion and facilitates the formation of dislocation tangles. MD simulations reveal that Re segregation leads to an extremely inhomogeneous distribution of stress components, which locally restricts dislocation movement. As a result, leading dislocations glide via a series of forward slip of local segments, forming a wavy dislocation line and reducing the dislocation slip velocity, thereby impeding dislocation motion. These findings enhance our understanding of synergistic strengthening effects in the nickel-based single crystal superalloys.