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Direct metal laser sintering (DMLS) is an additive manufacturing technique for the fabrication of near netshaped parts directly from computer-aided design data by melting together different layers with the help of a laser source. This paper presents an investigation of the surface roughness of aluminum samples produced by DMLS. A model based on an L 18 orthogonal array of Taguchi design was created to perform experimental planning. Some input parameters, namely laser power, scan speed, and hatching distance were selected for the investigation. The upper surfaces of the samples were analyzed before and after shot peening. The morphology was analyzed by means of field emission scanning electron microscope. Scan speed was found to have the greatest influence on the surface roughness. Further, shot peening can effectively reduce the surface roughness. KeywordsAluminum AlSi10Mg . Direct metal laser sintering (DMLS) . Taguchi method . Surface roughness Abbreviations AM Additive manufacturing DMLS Direct metal laser sintering CAD Computer-aided design SFF Solid freeform fabrication FFEs Fractional factorial experiments SLS Selective laser sintering S/N Signal to noise ratio ANOVA Analysis of variance FESEM Field emission scanning electron microscope BO Beam offset Nomenclature V Scan speed (millimeter per second) P Laser power (watt) h d Hatching distance (millimeter) E Energy density (joule per square millimeter) η L S/N calculated for larger-the-better response η S S/N calculated for smaller-the-better response R a Surface roughness (micrometer) 1 Introduction Additive manufacturing (AM) is the "process of joining mate-rials to make objects from 3D model data, usually layer upon layer" [1]. Therefore, AM makes it possible to build parts with very complex geometries directly from computer-aided design (CAD) models without any sort of tools or fixtures and with-out producing any waste material. Recently, demands for the direct manufacture of fullfunctional engineering metal com-ponents in different industry sectors such as motor racing, aerospace, pneumatics, automotive, and functional prototypes have increased greatly. One of the main SFF processes employed in AM is selective laser sintering (SLS). In this process, a part is built up layer by layer through the consoli-dation of powder particles with a focused laser beam that selectively scans the surface of the powder bed. Consolidation occurs either by actual fusion of the powder particles or by diffusion bonding. Laser sintering has been utilized to build parts from polymeric materials like

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The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM) technique known as Selective Laser Melting (SLM). This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented.

The directed energy deposition (DED) process can be employed to build net shape components or prototypes starting from powder or wires, through a layer-by-layer process. This process provides an opportunity to fabricate complex shaped and functionally graded parts that can be utilized in different engineering applications. DED uses a laser as a focused heat source to melt the in-situ delivered powder or wire-shaped raw materials. In the past years extensive studies on DED have shown that this process has great potential in order to be used for (i) rapid prototyping of metallic parts, (ii) fabrication of complex and customized parts, (iii) repairing/cladding valuable components which cannot be repaired by other traditional techniques. However, the industrial adoption of this process is still challenging owing to the lack of knowledge on the mechanical performances of the constructed components and also on the trustworthiness/durability of engineering parts produced by DED. This manuscript provides an overview of the additive manufacturing (AM) of titanium alloys and focuses in particular on the mechanical properties and microstructure of components fabricated by DED.

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In the circular economy, products, components, and materials are aimed to be kept at the utility and value all the lifetime. For this purpose, repair and remanufacturing are highly considered as proper techniques to return the value of the product during its life. Directed Energy Deposition (DED) is a very flexible type of additive manufacturing (AM), and among the AM techniques, it is most suitable for repairing and remanufacturing automotive and aerospace components. Its application allows damaged component to be repaired, and material lost in service to be replaced to restore the part to its original shape. In the past, tungsten inert gas welding was used as the main repair method. However, its heat affected zone is larger, and the quality is inferior. In comparison with the conventional welding processes, repair via DED has more advantages, including lower heat input, warpage and distortion, higher cooling rate, lower dilution rate, excellent metallurgical bonding between the deposited layers, high precision, and suitability for full automation. Hence, the proposed repairing method based on DED appears to be a capable method of repairing. Therefore, the focus of this study was to present an overview of the DED process and its role in the repairing of metallic components. The outcomes of this study confirm the significant capability of DED process as a repair and remanufacturing technology.

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