In Situ SEM-EBSD Tensile Study of GH4169 Alloy with Different Grain Sizes

To explore the effect of grain size on the tensile deformation mechanism of GH4169 nickel-based superalloy, specimens with average grain sizes of 10.7 μm and 70.6 μm were fabricated via different heat treatment processes, and in situ tensile experiments were carried out at room temperature using combined in situ SEM-EBSD technology. The results show that the fine-grained specimen exhibits a yield strength of 794 MPa and an ultimate tensile strength of 1372 MPa, while the coarse-grained specimen presents a yield strength of 317 MPa and an ultimate tensile strength of 782 MPa. During tensile loading, the fine-grained specimen undergoes uniform deformation with strong grain boundary coordination, accompanied by homogeneous grain orientation rotation; its average kernel average misorientation (KAM) value increases moderately from 0.82 to 0.89. In contrast, the coarse-grained specimen suffers severe inhomogeneous deformation and readily generates continuous slip bands, featuring abrupt local changes in grain orientation, with the KAM value rising from 0.8 to 1.04. Slip systems with high Schmid factors induce localized intragranular deformation. Benefiting from a high grain boundary density, the fine-grained specimen effectively restrains strain localization and achieves more uniform bulk deformation of the alloy.