Grain-size dependent elastic-plastic deformation behaviour of inconel 625 alloy studied by in-situ neutron diffraction

The effect of grain size on elastic-plastic deformation and twinning behaviour of Inconel 625 alloy was studied. Alloy samples were investigated using compressive deformation analysis, in-situ neutron diffraction, electron backscatter diffraction, and transmission electron microscopy. The alloy was found to exhibit strong elastic and plastic anisotropy. Grain refining was found to have several advantages, including the increased grain-specific diffraction elastic moduli, improved compatibility and homogeneity of polycrystalline deformation, and enhanced yield strength at room temperature. Two strong preferred orientations were present in coarse-grained samples: the Copper orientation of {112}<111>, in deformed grains because of dislocation slip, and the Brass orientation of {110}<112>, in elongated grains owing to deformation twinning. The coarse-grained samples also showed large quantities of stacking faults, multiple-slip lines, and dislocations. In contrast, stacking faults were not observed in fine-grained samples, however, a dense presence of slip lines, dislocations, and dislocation pile-ups at grain boundaries were observed. The fine-grained samples exhibited a higher density of dislocations than the coarse-grained samples given the same applied load during compressive deformation. The deformation mechanisms of the coarse-grained alloy were dominated by dislocation slipping and the formation of stacking faults, while the deformation of the fine-grained alloy showed only dislocation slipping.