The dislocation microstructure of a nickel-base single-crystal superalloy after tensile fracture

The dislocation microstructure after tensile deformation for a Ni-base single-crystal superalloy has been studied by transmission electron microscopy. The samples were strained to fracture at temperatures from room temperature to 1273 K. It was found that for deformation at intermediate temperatures, the dislocation microstructure was inhomogeneous due to the formation of dislocation concentrations with high-density tangling. These dislocation concentrations lie mainly along 〈1 0 0〉 or 〈1 1 0〉 directions, and extend over a length of a few micrometers. In addition, the structure of dislocation networks at the γ/γ′ interfaces formed at high temperature was also studied. Although previous studies have proposed basic configurations for these dislocation networks, the nature of a dislocation segment along the 〈0 1 0〉 direction was unresolved (Phil. Mag. A vol. 74 (1996) 229). In this work, high-resolution electron microscopy observation was used to study these dislocation networks. It was found that most of these segments are actually composed of two pairs of a/2〈1 1 0〉 dislocations with an average spacing of 8.5 nm, while only few of them are composed of single-line a〈1 0 0〉 dislocations.