Unveiling 3D sub-grain residual stresses in as-built additively manufactured steel using scanning 3DXRD

Non-destructive mapping of 3D microstructures in metal additive manufacturing (AM) remains challenging due to large orientation gradients and residual stress (RS) magnitudes. We leveraged scanning 3D X-ray diffraction (s3DXRD) to non-destructively resolve intragranular orientation-strain states and RS in laser powder bed fusion (L-PBF) SS316L for the first time. Type III von Mises RS displayed significant variation with proximity to grain boundaries, and in some locations, exceeded the macroscopic yield strength of L-PBF SS316L. Interestingly the spatial distribution of RS showed no correlation with orientation gradients, suggesting that stress relaxation during solidification is accommodated by lattice rotation. [GRAPHICS] .