Dislocation network with pair-coupling structure in {111} γ/γ′ interface of Ni-based single crystal superalloy

Abstract

The γ/γ′ interface dislocation network is reported to improve the high temperature creep resistance of single crystal superalloys and is usually found to deposit in {001} interface. In this work, a new type of dislocation network was found in {111} γ/γ′ interface at a single crystal model superalloy crept at 1100 °C/100 MPa. The dislocations in the network are screw with Burgers vectors of 1/2 a<110> and most interestingly, they exhibit a pair-coupling structure. Further investigation indicates that the formation of {111} interface dislocation network occurs when the γ′ raft structure begins to degrade by the dislocations cutting into the rafted γ′ through the interface. In this condition, the pair-coupling structure is established by the dislocations gliding in a single {111} plane of γ′, in order to remove the anti-phase boundary in γ′; these dislocations also act as diffusion channels for dissolving of the γ′ particle that is unstable under the interfacial stress from lattice misfit, which leads to the formation of {111}-type zigzag interface. The formation of this network arises as a consequence of more negative misfit, low-alloying γ′ particle and proper test conditions of temperature and stress.