*2.2. Microstructure Characterizations*

The samples used for metallographic observations were ground and polished using the conventional metallographic preparation technique, and the observation was then carried out using an optical microscope. TEM samples were prepared using the focused ion beam (FIB) technique with an FEI Quanta 3D FEG Dual Beam FIB scanning electron microscope following typical protocols. The microstructure and chemical composition analyses of both the as-processed and annealed samples were performed on an FEI Talos 200X analytical transmission electron microscope operated at 200 kV, equipped with a Super-X energy-dispersive X-ray spectroscopy (EDS) detector. The grain orientation analyses were performed using the NanoMegas ASTAR (to generate an electron backscattering diffraction (EBSD)-like automated crystal orientation map with 4-nm spatial resolution) setup installed in the Talos 200X TEM microscope, and data analyses were conducted using OIM Analysis software.
