Three-scale hierarchical P-rich microstructures via P doping: enhancing creep resistance significantly of a Ni-based single crystal model alloy

P microalloying is a promising alloy design strategy for superalloys due to its low cost and significant enhancement of creep resistance. Herein, the effects of P on microstructures and creep properties of a single crystal Ni-based model alloy were investigated during creep deformation at 650°C/60 MPa. The addition of P significantly improves the creep resistance through the formation of a three-scale hierarchical P-rich microstructure. First, solid-solution P atoms induce lattice misfit, resulting in atomic-scale strengthening. Second, the precipitation of nano-sized M3P phase effectively hinders dislocation movement, thereby achieving precipitation strengthening. Third, a kind of microscale strip-like structure forms during the creep process and significantly reduces the creep rate due to the interaction of P atoms and dislocations, which restricts dislocations sliding within itself and impeding dislocation slip in the matrix. The present work provides essential insights into the mechanism by which P influences the microstructure evolution and creep properties of designed single crystal superalloys.