On the anisotropy of thick-walled wire arc additively manufactured stainless steel parts

Wire Arc Additive Manufacturing (WAAM) is an emerging group of methods for producing large parts with complex geometries and varying wall thicknesses. These parts usually exhibit anisotropic material behavior due to their intrinsic heterogeneous microstructure. To fully exploit the versatility of WAAM, a rigorous understanding of the relationship between processing conditions, microstructure, and mechanical response of WAAM parts is necessary. To this end, this paper investigates the structure-property relationship for thick-walled austenitic stainless steel WAAM parts experimentally and numerically using a mean-field crystal plasticity model. The major microstructural features are studied using optical microscopy and electron backscattered diffraction. A representative microstructure volume element is obtained with averaged features to study spatial variations in the microstructure across the WAAM part. Uniaxial tensile tests assisted with Digital Image Correlation along the transverse direction, diagonal (45o from the transverse direction), and building direction within the transverse direction-building direction plane are used to study the mechanical properties and associated deformation fields. The resulting heterogeneous microstructure with periodically alternating microstructural features reveals a clear anisotropic material behavior. Furthermore, distinct plastic deformation patterns for different loading directions arise from the spatially varying microstructure. The proposed crystal plasticity model adequately describes the crystallographic texture-induced orientation-dependent yield strength.