Abstract
In recent times, additive manufacturing (AM) has proven to be an indispensable technique for processing complex 3D parts because of the versatility and ease of fabrication it offers. However, the generated microstructures show a high degree of complexity due to the complex solidification process of the melt pool. In this study, micromechanical modeling is applied to gain deeper insight into the influence of defects on plasticity and damage of 316L stainless steel specimens produced by a laser powder bed fusion (L‐PBF) process. With the statistical data obtained from microstructure characterization, the complex AM microstructures are modeled by a synthetic microstructure generation tool. A damage model in combination with an element deletion technique is implemented into a nonlocal crystal plasticity model to describe anisotropic mechanical behavior, including damage evolution. The element deletion technique is applied to effectively model the growth and coalescence of microstructural pores as described by a damage parameter. Numerical simulations show that the shape of the pores not only affects the yielding and hardening behavior but also influences the porosity evolution itself.
Highlights
Introduction occurdepending on the laser intensity, constant reheating and recooling of the previously melted layers take place
The complex porous microstructures used in this study have been synthesized using statistical data obtained from edge back scatter diffraction (EBSD) and light optical microscopy (LOM) micrographs
The nonlocal Crystal plasticity (CP) model,[26] originally developed to describe the hardening caused by strain gradients in polycrystal deformation, has been extended to include a damage evolution law to simulate material softening
Summary
The austenitic stainless steel AISI 316 (face-centered cubic crystal structure) was processed using L-PBF. For the EBSD investigations, an acceleration voltage of 21 keV and a working distance of 13 mm were used. During the EBSD measurements, the samples were tilted by 70 to the pole piece. The colors in the EBSD mappings represent the crystal directions in the surface normal direction (ND). The chemical composition was measured by means of spark emission spectrometry on compressed samples and is listed in Table 1 together with the nominal composition. Due to the spherical morphology and the low satellite density, the powder has a good flowability of 13.93 s/50 g (measured using a Hall Flowmeter according to DIN EN ISO 4490, t 1⁄4 22.4 C, air humidity 1⁄4 50.3%) and a bulk density of 4.34 kg dmÀ3 (measured according to DIN EN ISO 697)
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