In-situ observation of deformation behavior of the periodic structure in 316L stainless steel fabricated by wire and arc additive manufacturing

Abstract

Since the elongation of the side surface (perpendicular to the scanning direction) of the 316L block part fabricated by wire and arc additive manufacturing (WAAM) was seriously lower than that of the other surfaces, the in-situ electron backscatter diffraction method was used to study the deformation behaviors of the microstructure in this side surface. The results showed that the deformation and fracture of the periodic structure with alternating remelting areas (RA) and overlapping areas (OA) on this side surface depended on the competition of material hardening and deformation fracture. When the tensile direction was perpendicular to the periodic structure, the material deformation followed the isoload model. The more dispersed grain orientation in the RA induced dislocation packing and rotation of the austenite grains to activate multiple slip systems on both sides of the high-angle grain boundaries, which made the hardening rate of the RA higher than that of the OA. The strain was gradually concentrated in the OA, resulting in its local necking and fracture. When the tensile direction was parallel to the periodic structure, the material deformation followed the isostrain model. The rotation of the grains in the RA induced the formation of multiple slip systems and deformation twins. Therefore, the plasticity of the RA was higher than that of the OA, and the OA was preferentially necked and fractured.