The effect of the scanning strategy during selective laser melting (SLM) of Ti-6Al-4V was investigated. An optimized cellular scan strategy (island scan modeled) was compared to a simple cellular scan strategy (island scan stripes) and a simple antiparallel line scanning strategy (line scan). Surface texture was investigated by optical three-dimensional (3D) surface measurements, which when combined with light optical microscopy (LOM), revealed deflections caused by the thermal stresses during the build process. Elevated edges caused by the edge-effect dominate the surface texture of all investigated specimens. The scanning strategy determines the surface texture, and the lowest surface roughness was obtained by the line scan strategy. Porosity was investigated with X-ray computed tomography-imaging. Mainly spherical porosity was observed for the line scan and island scan modeled specimens, while the island scan stripes strategy showed more lack-of-fusion defects and a higher total porosity amount. Microstructure was investigated with LOM and scanning electron microscopy (SEM). The microstructure in Ti-6Al-4V was largely martensitic α’ and prior β grains. The morphology is different for the various scan strategies, and decomposition of α’ into lamellar α/β was observed in the bottom part of the island scan specimen. Accordingly, the hardness decreased in the decomposed part of the specimen.

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Wire arc additive manufacturing (WAAM) direct energy deposition is used to process two different duplex stainless steels (DSS) wire chemistries. Macro- and micromechanical response variables relevant to industrialization are studied using a design of the experiment (DoE) approach. The tested operation window shows that the variation of layer height and over-thickness are highly correlated with travel speed and wire feed speed and positively correlated with heat input. The maximum achieved average instantaneous deposition rate is 3.54 kg/h. The use of wire G2205, which contains 5 wt% nickel content, results in a ferrite-to-austenite ratio that is equally balanced, while wire G2209, with 9 wt% nickel, provides a lower ferrite content. The spatial distribution of Fe% is influenced by part geometry and path planning, and higher heat inputs result in coarser microstructures. The manufacturing weaving strategy generates a heterogeneous microstructure characterized by fluctuations in Fe%. Thus, understanding the effect of complex thermal history, higher-dimensional design spaces, and uncertainty quantification is required to drive metal WAAM toward full industrialization.