Substructures and microsegregation ofγ/γlaths are analyzed with HRTEM and HAADF-STEM. Results show that the substructures are generated during evolution of shear transformation on the(111-)plane ofγlath. At the beginning, shear transformation evolves in a singleγlath, and a superstructure intrinsic stacking fault (SISF) forms in theγlath. After the formation of the SISF, the shear transformation may evolve in two different ways. If the shear transformation evolves into neighboringγlaths, the

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... F also penetrates into neighboringγlaths and a ribbon of SISFs forms. If shear transformation continues to evolve in the original lath, complex substructures begin to form in the original. If shear transformation in the original lath is homogeneous and complete, secondary twin forms which may further grow into twin intersection. Incomplete shear transformation could not form secondary twins but generates a high concentration of planar faults on the(111-)plane. These planar faults may further penetrate theγ/γlath interface, grow into adjacent laths, and form a ribbon of planar faults.