Mapping residual stresses in AlSi10Mg alloy fabricated by powder bed fusion-laser beam method

Residual stresses in metal alloys fabricated by the powder bed fusion-laser beam (PBF-LB) method exhibit anisotropy influenced by laser scanning and building orientations. This study maps nanoscale residual stresses within a single grain of PBF-LB AlSi10Mg alloy using various transmission electron microscopy (TEM) modalities. Residual stress maps were obtained for both as-built and T6 heat-treated samples along scanning and building orientations. Post-analysis revealed that T6 heat treatment reduced tensile stress compared to as-built samples. For example, in the [1̅00] crystallographic direction, average tensile and compressive residual stresses in the building direction decreased by ~ 70% after T6 treatment. Anisotropy in residual stresses was also observed; in the [1̅00] direction, average residual stresses in scanning orientation were ~ 13% and ~ 23% higher than the building direction in as-built and T6-treated samples, respectively. Heat treatment effects were further examined using image-based finite element method (FEM) simulations to understand the stress-driven mechanisms behind Si eutectic break-up and Si precipitate diffusion into the Al matrix. The results revealed regions of tensile and compressive stress within Si eutectic zones, identifying them as sources for Si diffusion and nucleation of Si-based precipitates within the matrix.