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The effect of processing parameters on the mechanical properties of AISI 304L stainless steel components fabricated using laser-based directed energy deposition additive manufacturing (AM) was investigated. Two walls were fabricated, with high linear heat inputs of 271 and 377 J/mm, to determine the effect of processing parameters on microstructure and mechanical properties of 304L made by AM. Uniaxial tension tests were performed on samples extracted from the walls in longitudinal and transverse directions. The yield strength, ultimate tensile strength, and ductility, were higher in the lower linear heat input wall compared to the higher linear heat input wall. The ductility in the longitudinal direction was less than that in the transverse direction, while there was no clear anisotropy in strength. A grain growth model adapted from welding was used to interpret and predict the grain sizes in the walls as a function of processing parameters and position. A Hall-Petch relationship was used to explain the effect of local grain size and morphology on the location-and direction-dependent yield strengths in

Many engineering applications, particularly in extreme environments, require components with properties that vary with location in the part. Functionally graded materials (FGMs), which possess gradients in properties such as hardness or density, are a potential solution to address these requirements. The laser-based additive manufacturing process of directed energy deposition (DED) can be used to fabricate metallic parts with a gradient in composition by adjusting the volume fraction of metallic powders delivered to the melt pool as a function of position. As this is a fusion process, secondary phases may develop in the gradient zone during solidification that can result in undesirable properties in the part. This work describes experimental and thermodynamic studies of a component built from 304L stainless steel © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ incrementally graded to Inconel 625. The microstructure, chemistry, phase composition, and microhardness as a function of position were characterized by microscopy, energy dispersive spectroscopy, X-ray diffraction, and microindentation. Particles of secondary phases were found in small amounts within cracks in the gradient zone. These were ascertained to consist of transition metal carbides by experimental results and thermodynamic calculations. The study provides a combined experimental and thermodynamic computational modeling approach toward the fabrication and evaluation of a functionally graded material made by DED additive manufacturing.