Stress driving element redistribution and rafting of γ′ phase in Ni–Al–Mo superalloy

Servicing as the blade of aircraft engine, Ni-based superalloys suffer the axis stress in working. Driven by the creep strain energy, the γ′-Ni3Al precipitates will be rafted via the element diffusion in Ni-based superalloys, and the rafting of γ′ phase has great effects on the creep properties of the superalloys. By coupling the sublattice free energy and crystal plasticity model, the phase-field modeling is performed to investigate the evolution kinetics of γ′-Ni3Al phase in the Ni–15Al–2Mo (at.%) superalloy under creep stress, and the elements directional diffusions between the γ/γ′ phases are revealed. The increase of Al concentration and the decrease of Mo concentration in the γ channel both promote the directional connection of γ′ phase. An initial stage increase in partition coefficient of $$K_{{{ ext{Mo}}}}^{{gamma^prime/gamma }}$$ indicates that the fast rafting rate of γ′ phase repulses the Mo to the connection area of γ′ phases. The effects of diffusion potential including elastic potential and chemical potential on the diffusion and rafting of γ′ phase are clarified. The elements directional diffusion between γ/γ′ phases is driven by the difference of chemical potential and elastic potential between γ phase and γ′ phase, and the elastic contribution to the diffusion of Mo is larger than that of Al and plays a leading role in the rafting of γ′ phase.