Localized deformation and failure mechanism in TIG-welded wire-arc additively manufactured 304 stainless steel: An in-situ synchrotron XRD study

To enable the fabrication of complex structural components, this study investigates the post-weld microstructureand mechanical properties of wire arc additively manufactured (WAAMed) 304 stainless steel. The investigationemploys both EBSD and in-situ synchrotron X-ray diffraction (SXRD) techniques. The research reveals grain sizevariations across the processed material (heat-affected zone (HAZ) vs fusion zone (FZ)), as well as differences inthe kernel average misorientation (KAM) among the different regions that coexist in the material. During tensiledeformation, the material underwent sequential martensitic transformation following the γ → ε → α′ sequence,with the FZ demonstrating greater elongation (approximately 64%). Strain accommodation is achieved throughthe synergistic interaction of dislocation slip and martensitic transformation. In-situ SXRD analysis reveals thatduring loading, the dislocation density increases to varying degrees across different regions (FZ, HAZ, and basemetal (BM)), indicating the occurrence of coordinated deformation within the material. Ultimately, fractureoccurs in the BM region under the combined effect of its high KAM value and the continuous increase inα′-martensite content under high local dislocation density.