Mechanical Testing and Microstructural Analysis of Wire Arc Additively Manufactured Steels

Wire arc additive manufacturing (WAAM) is a metal 3D printing method that allows the cost-effective and efficient production of large-scale elements, and has thus gained great interest from architects and structural engineers. Integration of this novel technology into the construction industry, however, requires the development of a clear understanding of the mechanical behaviour of WAAM materials. To this end, a comprehensive experimental study into the mechanical properties and microstructure of WAAM plates made of normal- and high-strength steels has been undertaken and is reported herein. A total of 137 as-built and machined tensile coupons were tested, extracted in various directions relative to the print layer orientation from WAAM plates of two nominal thicknesses, built using different deposition strategies. Microstructural characterisation was also performed by means of optical microscopy and electron backscatter diffraction (EBSD). The EBSD analysis revealed a weak crystallographic texture, which explained the observed mechanical properties being almost isotropic. The geometric undulations of the as-built coupons resulted in some reduction in effective mechanical properties and a degree of anisotropy. Overall, the examined WAAM material exhibited consistent mechanical properties, a Young’s modulus comparable to conventionally-produced steels, marginally lower strength, reflecting the slower cooling conditions than is customary, and good ductility.