Transformation microstructure and nucleation crystallography in high Sc-contained Al–Sc alloys after laser treatment

The high Sc-alloyed Al–Sc sputtering target is applied to produce Sc-doped AlN (Al_1−xSc_xN) thin films through reactive magnetron sputtering. The sputtering process demands Al–Sc sputtering targets with fine and stable grain sizes featuring random orientations. In this work, laser treatment with varying scanning speeds is applied to the Al-(10 at.%, 20 at.%) Sc alloys, and the microstructure is characterized using the electron backscatter diffraction (EBSD) method and transmission electron microscopy (TEM). The results indicate that the laser treatment enhances the solubility of Sc in the matrix; however, the nucleation crystallography during solidification differs among these alloys. Epitaxial growth is observed in Al–20Sc, remaining a large grain size with different scanning speeds. In contrast, Al–10Sc exhibits refined grain sizes, reduced to about 2 μm compared to 200 μm in the as-casted alloy. Laser treatment generates more than 40% twin boundaries, leading to the randomization of the texture and refinement of the grain size through twin variants. This study demonstrates the feasibility of grain boundary engineering for Al–10Sc sputtering targets through laser scanning.