Creep deformation related to dislocations cutting the γ′ phase of a Ni-base single crystal superalloy

The microstructures of a Ru-containing single crystal superalloy have been characterized after creep deformation at 1000 °C under 270 MPa, 290 MPa and 310 MPa and at 1140 °C under 120 MPa, 137 MPa and 150 MPa. Detailed analysis demonstrates that the width of the rafted γ′ phase at 1140 °C is wider than that at 1000 °C. The gradually disappeared γ matrix has been observed at 1000 °C in the ruptured specimens; however, this case has been rarely observed at 1140 °C. On the other hand, the topological inversion has taken place under present creep conditions. Furthermore, under all the creep conditions conducted in this work, the a0 〈010〉 superdislocations in the γ′ phase have been observed in this experimental alloy. These superdislocations usually possess non-compact core which consists of two a0/2〈101〉 dislocations with different Burgers vectors. At 1000 °C, only the long dislocations which mainly orientate the 〈110〉 directions (dislocation line direction) have been observed; however, at 1140 °C, both the long and zigzag (partial with non-compact core and mainly orientated the 〈110〉 and 〈100〉 directions) superdislocations have been observed. Apart from that, a special superdislocation with two segments of compact core and two segments of non-compact core has been observed, which has been rarely reported previously. At last, a very interesting observation is that a superdislocation array presents in the rafted γ′ phase after creep at 1140 °C under 150 MPa. The formation process and configuration of this dislocation array have been analyzed in detail, which has also been rarely reported previously.