In situ 3D reciprocal-space mapping of misorientation evolution during creep of a single-crystal Ni-based superalloy

This work investigates the evolution of crystal misorientation, also referred to as mosaicity , in a single-crystal Ni-based superalloy during high-temperature, low-stress creep using in situ three-dimensional reciprocal-space mapping. Initial misorientation between neighboring dendritic domains are small (typically < 1 − 1.2 ° ), and heating alone produces no measurable changes in the mosaic structure. In contrast, loading and subsequent creep at 1000 °C and 1050 °C induce pronounced evolution: individual orientation domains rotate, broaden, and progressively merge into an apparent extended orientation domain. At 950 °C, mosaicity changes remain limited, consistent with reduced plastic activity. Although domain rotation trajectories exhibit similar trends, they display distinct rotation rates, which may result from small differences in resolved shear stress associated with local crystallographic misorientation, together with local microstructural heterogeneities. Notably, the mosaic structure established during creep is retained after unloading and cooling to room temperature. These results demonstrate that mosaicity evolves actively during creep and provide direct evidence of a mesoscale crystallographic response associated with heterheterogeneous plastic deformation in single-crystal Ni-based superalloys.