Impact of Secondary γ’ Precipitate on the High-Temperature Creep Properties of DD6 Alloy

The article elucidates the precipitation behavior of the secondary γ’ precipitates and its influence mechanism on the creep properties of DD6 alloy during creep at 1100 ℃ / 137 MPa, employing high-resolution transmission electron microscopy and scanning electron microscopy. The alloy exhibits an N-type raft structure under varying creep times, with a mismatch between the γ and γ’ phases ranging from − 0.06% to − 0.59%. A significant amount of secondary γ’ precipitates, predominantly spherical or cubic in shape, is dispersed in the matrix, with sizes decreasing gradually from the center of the γ matrix channel to the γ/γ’ interface, and randomly distributed in the matrix channels. Dislocations are discretely distributed in the γ matrix channel, which, upon encountering the secondary γ’ precipitates, impedes their movement, leading to the transformation of the initially dense dislocation network into an irregular one. Moreover, numerous small secondary γ’ precipitates particles can absorb dislocations. Approximately every 170 to 1628 atomic spacings of the secondary γ’ precipitates can accommodate a misfit caused by an edge dislocation. The widespread presence of secondary γ’ precipitates in the γ matrix effectively disrupts dislocation networks, significantly shortening the creep life of the alloy.