Effect of build orientation on fracture and tensile behavior of A357 Al alloy processed by Selective Laser Melting

Selective Laser Melting (SLM) is an additive manufacturing technology that allows producing components through local melting of a metallic powder bed using high-power laser beam in accordance with 3D digital CAD models. Cast Al-Si-Mg alloys are broadly used due to their good processability by SLM and mechanical properties. This work investigates the mechanical behavior of A357 aluminum alloy produced by SLM in the as built and artificially aged conditions. In particular, the tensile properties and fracture toughness of the alloy were investigated according to different specimen orientations on the build plate in the first case and different crack propagation planes in the second. In addition, microstructural and fractographic analyses were performed in order to investigate crack propagation paths and fracture mechanisms. The results showed that building orientation has a strong influence on material response, mainly with regards to the fracture toughness. The melt pool boundaries act as preferential paths for crack propagation and lead to a marked drop in fracture toughness of samples with cracks perpendicular to the building direction.