FIB-SEM analysis of local residual stresses due to laser scanning for additive manufacturing

This study investigates local residual stress formation in a wrought Ni-based alloy plate subjected to laser scanning under power and speed conditions near the optimal LPBF fusion window. A full factorial experiment design was implemented, generating nine melt pool regimes by varying laser power and scan speed. Melt pools and adjacent heat-affected zones (HAZ) were revealed using electron backscatter diffraction (EBSD), while residual stresses were quantified with ∼50 μm resolution via focused ion beam ring-milling and digital image correlation (FIB-DIC). Experimental results showed stresses ranging from –500 to +500 MPa for σ yy and σ zz along the melt pool depth, with predominantly tensile stress states across the width close to the sample surface. Tensile stresses were concentrated near the laser interaction zone, while compressive states developed deeper in the melt pool. Higher linear energy density expanded the tensile regions at the surface and into the sample depth, and intensified the compressive zones below. An analytical framework based on the Rosenthal and Eagar–Tsai heat conduction solutions coupled with thermoelastic plastic models reproduced FIB-DIC results within 5–10 %. While the FIB-DIC technique is inherently sensitive to micro-scale Type II–III stress variations that depend on grain morphology, this study emphasizes process-level regularities. Since FIB-DIC recovers Type I–II–III stresses, but only Type I reveals global trends, the measurements are here interpreted at the macroscopic Type I level to establish transferable patterns. The combined approach strengthens the process-residual stress linkage for laser treatment and LPBF, enabling rapid parameter optimization and stress management informed build strategies. • Local residual stress dependence on LPBF scanning regime in Ni-superalloy established • EBSD mapping revealed melt pool and HAZ morphology after laser scanning • Local melt pool residual stress quantified by combined FIB-DIC and analytical modeling