An X-Ray Laue Diffraction Study of Relative Lattice Rotation and Local Orientation Gradient in a Single-Crystal Superalloy

Nickel-based single-crystal superalloys significantly enhance creep rupture strength and high-temperature stability due to their structural advantage of eliminating grain boundaries. Plastic strain can be induced in the single-crystal superalloys during investment casting and cooling, which provides a sufficient driving force for recrystallization during subsequent postcasting heat treatment. In this study, a single-crystal superalloy is stretched along the primary dendrite growth direction (parallel to [001]) with different plastic strains to simulate the deformation induced during investment casting. X-ray Laue diffraction and transmission electron microscopy are performed to study the structural evolutions in the single-crystal superalloys during tensile deformation and subsequent annealing. The (Formula presented.) slip system is activated in the single-crystal superalloy during tension along [001] direction. A nonuniform distribution of local orientation gradient is observed in the deformed specimens, where slip steps and slip bands are detected with a high kernel averaged misorientation (KAM) ranging from 0.5° to 1°. After annealing treatment, the mean KAM angle is still large but the number fraction of the KAM exceeding 0.5° is reduced when compared to the corresponding deformed state. The relative lattice rotation induced by the plastic deformation is unchanged after annealing treatment.