316L austenitic stainless steel thin-walls fabricated via Arc-Based directed energy deposition: Constitutive model description of anisotropic mechanical properties

Directed Energy Deposition (DED) technology has advantages in engineering industry due to its fast-forming speed and ability to produce large parts. 316 L stainless steel has been widely used in seismic and fire resistance of steel structures and marine engineering due to its high ductility, fire resistance and corrosion resistance. However, the mechanical anisotropy of DED printed steel plate has not been systematically explained, and the experimental data for reference is relatively scarce, which limits the application of this technology in engineering. This paper presents uniaxial tensile test, metallographic test, X-Ray Diffraction (XRD) test, and semi-in situ Electron Backscattered Diffraction (EBSD) test on 316 L stainless steel plates via DED process in 0 degrees, 45 degrees, and 90 degrees orientations to the build platform. The anisotropy of elastic modulus, Poisson's ratio, yield strength, tensile strength and ductility of the material was evaluated by mechanical experiments. The phase composition, crystallographic texture and deformation mechanism were analyzed by microscopic characterization experiments. The results were used to analyze the relationship between macroscopic mechanical properties and microstructure, and it is found that grain morphology, inter-dendritic and single crystal properties are the main causes of mechanical anisotropy. The anisotropic constitutive model is calibrated by the experimental results, and it can characterize the elastic and inelastic anisotropy behavior of DED 316 L plate well. This study provides a method to explain the mechanical anisotropy behavior of DED manufactured parts and provides data support for the constitutive model, which can be used for the study of anisotropic behavior of other additive manufacturing processes, the formulation of design specifications and the possibility of controlling anisotropic behavior through process parameters.