Investigation of the effect of laser shock peening in additively manufactured samples through Bragg Edge neutron imaging

Morgano, M.*; Kalentics, N.*; Carminati, C.*; Capek, J.*; Makowska, M.*; Woracek, R.*; Maimaitiyili, T.*; Shinohara, Takenao   ; Loge, R.*; Strobl, M.*

Additive manufacturing is a promising and rapidly rising technology in metal processing. However, besides a number of key advantages the constitution of a part through a complex thermo-mechanical process implies also some severe issues with the potential of impacting the quality of products. In laser powder bed fusion (LPBF) the repetitive heating and cooling cycles induce severe strains in the built material, which can have a number of adverse consequences such as deformation, cracking and decreased fatigue life that might lead to severe failure even already during processing. Here we demonstrate how lattice strains implied by LPBF and laser shock peening (LSP) can efficiently be characterized through diffraction contrast neutron imaging. Despite the spatial resolution need with regards to the significant gradients of the stress distribution and the specific microstructure, which prevent the application of more conventional methods, Bragg edge imaging succeeds to provide essential two-dimensionally spatial resolved strain maps in full field single exposure measurements.