Microscopic insights into the mechanical behavior of a Ni-Co-based superalloy through in-situ neutron diffraction

The micromechanical behaviors and dislocation evolution in a polycrystalline Ni-Co-based superalloy were systematically investigated by in situ neutron diffraction tensile testing combined with line profile analysis. The results reveal the sequential activation of γ’ shearing and Orowan looping mechanisms, with interphase load partitioning governed by strain-dependent interactions of dislocation and precipitate. During the initial plastic deformation, the γ and γ’ phases undergo co-deformation through dislocation shearing without load transfer, while the Orowan looping facilitates the load transfer from γ to γ’ phase at a higher strain level. Furthermore, the low stacking fault energy leads to a rising fraction of screw dislocations by suppressing cross-slip. Crucially, the pinning effect of γ’ precipitates hinders the rearrangement of these dislocations into low-energy structures, resulting in the formation of high-energy, weakly screened dislocation configurations. These findings provide new evidence for the planar slip dominance in Ni-Co-based superalloys, enabling quantitative assessment of microstructural evolution and micromechanical responses.