Influence of the printing strategy on the microstructure and mechanical properties of thick-walled wire arc additive manufactured stainless steels

Stainless steels manufactured via wire-arc additive manufacturing (WAAM) often exhibit heterogeneous and strongly textured microstructures, usually entailing an anisotropic mechanical response. These microstructures are induced by the processing conditions, such as specific printing strategies. The influence of three different printing strategies on the microstructure and mechanical properties of thick-walled stainless steel parts is investigated in this work. The three strategies considered are layer-wise unidirectional, layer-wise weaving, and bidirectional zig-zag scanning paths. The microstructure of the samples is characterized at different scales using optical microscopy and electron backscattered diffraction. The mechanical behavior is studied by uniaxial tensile tests, assisted with digital image correlation, on specimens extracted at different orientations. In addition, a mean-field crystal plasticity model is used to study the macroscopic yield strength anisotropy. The results reveal different microstructures, especially crystal orientations and grain size, resulting in distinct orientation-dependent mechanical properties and plastic deformation behavior. The layer-wise unidirectional and weaving strategies exhibit a significant plastic anisotropy, especially regarding ductility. In contrast, the bidirectional zig-zag strategy shows a comparatively homogeneous microstructure and more isotropic mechanical behavior than the other two printing strategies. Additionally, the predictions from a mean-field crystal plasticity model reveal the three-dimensional anisotropic yield strength trends, showing a correlation between the < 111 > crystal directions and the strongest yield response for all samples.