ABSTRACT:
In-situ experimental techniques are essential for understanding the deformation evolution of materials by enabling real-time tracking of microstructure changes. This study employs in-situ electron backscatter diffraction (EBSD), high-resolution digital image correlation (HR-DIC), and in-situ neutron diffraction to investigate the deformation mechanism of IN690. The results reveal that the geometrically necessary dislocation (GND) density does not increase during elastic deformation but exhibits a linear increase during plastic deformation when the strain is less than 10%. Initially, during the onset of plastic deformation, GND density primarily accumulates along grain boundaries, with high-density areas developing within grains as deformation progresses. Careful analysis shows that the free surface effect during deformation does not impact GND density measurements. High resolution digital image correlation (HR-DIC) shear strain maps demonstrate local strain heterogeneity, with long and intense slip traces observed near twin boundaries and an increase in number and intensity of slip traces as deformation progresses. In-situ neutron diffraction indicates that the total dislocation density of IN690, which includes statistically stored dislocations (SSD) and remains unchanged during elastic deformation and increases linearly during plastic deformation. The GND density measured by EBSD constitutes less than 7% of the total dislocation density measured by neutron diffraction.
