The formation of intragranular stress concentration in plastic deformed Ni-base superalloy: Governing factors and process

For Ni-base superalloy, the creep property is still vital. Polycrystalline Ni-base superalloy samples with different creep strain are investigated by electron backscatter diffraction along with phase field simulation to analyze the formation of intragranular stress concentration (ISC) with respect to the governing factors and process. The results show that ISCs are more likely to form at vicinity of grain boundaries (GBs) because of the multiple-slips near GBs which are activated by the mediated stress at GBs. The frequency of ISCs near the GBs decreases first at low strain and then increases with increasing strain because of the formation and destroy of stress concentrations in grain interior. The ISCs are more likely to form at vicinity of the GBs with misorientation of 45°–55°, independent of the strain. In addition, the GBs parallel or perpendicular to the loading direction will not emit dislocations to activate multiple-slips near GBs when the strain is small because of their triaxial stress state. As the strain increases, these GBs begin to emit dislocations because of the change of stress state or the formation of ‘weak points’. The GBs perpendicular to the applied stress own the highest probability when the strain is 9.38%. Our results provide unique and critical data to support future optimization of alloy properties and the development of new alloys.