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

The article elucidates the precipitation behavior of the secondary gamma' precipitates and its influence mechanism on the creep properties of DD6 alloy during creep at 1100 degree celsius / 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 gamma and gamma' phases ranging from - 0.06% to - 0.59%. A significant amount of secondary gamma' precipitates, predominantly spherical or cubic in shape, is dispersed in the matrix, with sizes decreasing gradually from the center of the gamma matrix channel to the gamma/gamma' interface, and randomly distributed in the matrix channels. Dislocations are discretely distributed in the gamma matrix channel, which, upon encountering the secondary gamma' precipitates, impedes their movement, leading to the transformation of the initially dense dislocation network into an irregular one. Moreover, numerous small secondary gamma' precipitates particles can absorb dislocations. Approximately every 170 to 1628 atomic spacings of the secondary gamma' precipitates can accommodate a misfit caused by an edge dislocation. The widespread presence of secondary gamma' precipitates in the gamma matrix effectively disrupts dislocation networks, significantly shortening the creep life of the alloy.