Navigating the unavoidable: Enhancing the EBSD indexability through adaptation to three hurdles in femtosecond laser...

Femtosecond (fs) laser milling offers exceptionally rapid material removal for cross-section preparation; however, its application to electron backscatter diffraction (EBSD) is limited by three critical hurdles: (i) laser-induced periodic surface structures (LIPSS), (ii) curtaining typically caused by surface morphology, leading to uneven milling, and (iii) taper angle deviations from the nominal geometry. In this study, we systematically evaluate the impact of these three hurdles on EBSD performance using large-area cross-sections prepared in 304 stainless steel. High fluence milling (11.3 J/cm²) followed by reduced fluence polishing (4.5 J/cm²) produced LIPSS (±100 nm amplitude) along with the formation of curtaining and a taper angle. Among these, the taper angle was identified as the dominant factor controlling indexing efficiency. Increasing the tilt angle from 70° to 76.5° improved the EBSD hit rate from 41.5% to 74.1%. Dynamic template matching confirmed enhanced correlation between simulated and acquired patterns, with the mean cross-correlation coefficient increasing from 0.22 to 0.28. LIPSS introduced nearly vertical periodic misorientation gradients exceeding ±2°. Detailed pixel-by-pixel analysis of EBSD patterns confirmed that the non-indexing was likely caused by surface topology associated with the LIPSS. While these hurdles currently limit the full reliability of EBSD and the extraction of advanced information (e.g., misorientation maps) without artefacts, the results demonstrate that fs-laser preparation can be engineered to enable rapid grain structure characterisation of deeply buried regions. Understanding and controlling these three barriers provides a pathway toward large-area EBSD sample preparation for microstructural analysis.