Creep deformation related to γ′ phase cutting at high temperature of a [111] oriented nickel-base single crystal superalloy

The configurations of superdislocations in a [111]-oriented nickel-base single crystal superalloy have been investigated after creep deformation at 1100 degrees C/150 MPa. The superdislocation arrays and hexagonal super dislocation networks are formed in irregular rafted gamma' phase, which are rarely observed in [001] crept specimens. It is believed that the superdislocation networks are formed by reactions of superdislocation arrays and another kind of superdislocations. Careful diffraction contrast analysis shows that the Burgers vector of the super-dislocation arrays is a [01 (1) over bar], which is not the favorable slip system when loaded along [111]. The formation of the arrays is supposed to be related to the matrix dislocations cross slipping in two {001} channels and the stress concentration caused by inhomogeneous rafted structures. The networks in gamma' phase may prevent dislocation movement and slash the increase of creep rate to some extent.