Mechanical properties, microstructural characteristics and heat treatment effects of WAAM stainless-steel plate material

Wire and arc additive manufacturing (WAAM) is a technology that enables the in-situ manufacturing of large-scale components efficiently for the construction industry. However, uncertainties persist regarding the characteristics of WAAM materials, such as anisotropic mechanical properties and their correlation with metallographic structure and fracture morphology, printing paths, and heat treatment. More experimental data is also required to establish design methods for the application of WAAM stainless steel in construction. To bridge these knowledge gaps, a comprehensive series of tensile tests was therefore conducted on WAAM stainless steel. Four deposition plates were fabricated using WAAM technique with different printing paths, and tensile coupons were extracted in three directions from each plate. Tensile tests were conducted to evaluate the mechanical properties of the material. Optical microscopy (OM) and scanning electron microscopy (SEM) were then employed to examine the metallographic structure of the material and the fracture morphology of the coupons. The results showed that the WAAM material had good yield and ultimate strengths but slightly lower ductility than conventional stainless steel. Anisotropy was observed in some but not all printing paths, and Young's modulus, ultimate strain and fracture strain exhibited the highest values in the 45° specimens. The grain size of the plate was influenced by its printing path. Mechanical properties were associated with the metallographic structure and fracture morphology. Compared to the heat-treated counterpart, the non-heat-treated material exhibited higher yield and ultimate strengths but lower ductility.