Orientation dependence of dislocation structures and deformation mechanisms in creep deformed CMSX-4 single crystals

Transmission electron microscopy investigations have been carried out in single crystal creep specimens of the nickel-based superalloy CMSX-4, deformed to different stages of their creep lives. The microstructural background of creep anisotropy was observed at 1123 and 1253 K. At the lower temperature, the pronounced creep anisotropy can be attributed to the superposition of coherency and external stresses, leading to different dislocation configurations. At the higher temperature, the creep anisotropy for [001] and [011] load axes is reduced by γ′ rafting in these orientations.