Anisotropic yield surfaces of additively manufactured metals simulated with crystal plasticity

Abstract

The mechanical anisotropy created by additive manufacturing (AM) is not yet fully understood and can depend on many factors, such as powder material, manufacturing technology and printing parameters. In this work, the anisotropic mechanical properties of as-built, laser powder bed fusion (LPBF) austenitic stainless steel 316L and titanium alloy Ti-6Al-4V are investigated through crystal plasticity simulations. Periodic representative volume elements (RVEs) are used that are specific to each material. The RVE for austenitic stainless steel consists of FCC crystals with a crystallographic texture measured by X-ray diffraction. The α′ martensite microstructure of Ti-6Al-4V is captured with a multi-scale RVE, including internal lamellar structures, using HCP crystals and a synthetically generated texture. For both materials, the crystal plasticity parameters are calibrated against tensile tests carried out on dog-bone specimens printed in different orientations. The RVEs, calibrated to experiments, are applied in virtual material testing and subjected to multiple load cases to generate the Hill-48 and Yld2004-18p yield surfaces of the materials.