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Pore defects inescapably occur during the selective laser melting (SLM) process of metallic materials, which are difficult to be eliminated even by advanced process optimizing and post-treatment technologies. Properties of SLM-fabricated materials depend on the influence of pores, while the effect mechanism is not clearly understood. To clarify the pore effects and achieve reliable forecasting, a statistical-theory-based grain-scale simulation work was performed. Taking Inconel-718 as the example, actual pore defects were detected and classified into three types i.e., gas pore, keyhole pore and lack-of-fusion (LOF) pore, which were then fitted by single or multiple ellipsoids. The volume, shape and posture of pores were characterized by independent parameters, and single-pore-included single-crystal simulations were carried out. Furthermore, overall pore effects were divided into single-ellipsoidal effects, sub-pore quantity effects and sub-pore intersection effects, and the influence mechanisms of pore characteristics on the mean tensile strength and the maximum damage driving force were clarified through partial correlation analysis. Eventually, single-crystal mechanical and damage property prediction models for the grain with an internal pore defect were developed and verified, which show good accuracy with 8–22% relative deviation for damage resistance predictions, and show excellent accuracy with lower than 0.3% relative deviation for strength property predictions. |
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