The Atomic Segregation and Ordered Stacking Fault Phase Transformation Along the Superlattice Stacking Fault During Creep in a Novel Powder Metallurgy Ni-Based Superalloy

Superlattice stacking faults (SSFs) in the γ′ precipitate of a novel powder metallurgy (PM) Ni-based superalloy after creep rupture at 760 °C/552 MPa are analyzed through atomic-level characterization. The results show that the Cottrell atmosphere formed by the segregation of γ formers Cr, Co, and Mo near the leading partial dislocation drives the extension of SSFs. Co, Cr, Mo, and W segregate along the superlattice intrinsic stacking fault and lead to the formation of the ordered stacking fault phase ε-D0₁₉. Meanwhile, Co, Ti, W, and Nb segregate along the superlattice extrinsic stacking fault and promote the formation of the ordered phase η-D0₂₄. In addition, the formation process diagram of the SSF with ordered phase under the aid of segregation is drawn. The transformation of the ordered stacking fault phase can be evaluated by the atomic ratios of Al over the stacking fault phase formers.