Residual stresses in additively manufactured AlSi10Mg: Raman spectroscopy and X-ray diffraction analysis

Metal parts produced by Additive Manufacturing, and in particular Laser Powder Bed Fusion (LPBF), suffer from residual stresses due to high thermal gradients causing cyclic expansion and contraction of the alloy. This work deals with the determination of residual stress in rapidly solidified AlSi10Mg samples using two non-destructive techniques: Raman spectroscopy, rapid, unconventional but applicable to Al[sbnd]Si alloys, and XRD (ω-method), used as benchmark, being a classical method for determining residual stresses. Al stress level was studied by XRD both on the surface of LPBF samples and in the interior, after in-depth sectioning. Raman was employed to assess the stress on Si. The effect of particle size and stress on the Raman was separated determining the size distribution of Si particles, making Raman suitable to study residual stresses in alloys containing free Si. Al and Si stresses were evaluated also by means of the Williamson-Hall method: stresses are of tensile type with agreement among all methods. Considering the alloy as a composite, stress on Si was estimated using the Eshelby's model, showing that larger eutectic particles undergo lower stress with respect to nanometric precipitates.