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Alumina toughened zirconia (ATZ) parts were produced via a laser-based powder bed fusion technology using a conventional Nd-YAG continuous wave laser. The powder was produced using a spray drying process and the laser matter interaction was enhanced by a binder pyrolysis. A processing window led to part densities of over 90 %. Thermal post-processing to further increase the part density was investigated using dilatometry. The microstructure was analysed using X-ray powder diffraction measurements. The mechanical properties were assessed using a four-point bending test on ten specimens, reaching a bending strength of 31 ± 11 MPa.

This paper deals with the research of the Selective Laser Melting (SLM) scanning strategy to produce lattice structures from AlSi10Mg powder material. Nowadays, most of the SLM end-users use the laser strategy and parameters recommended by powder or machine suppliers to produce different components. However, this setup can cause material and shape imperfection, especially in the case of low-volume lattice structures. In this study, the default meander scanning strategy for AlSi10Mg material was changed to contour strategy and its main SLM process parameters were developed. Commonly used experiments were modified to consider the lattice structure's shape and dimension. The results showed that by using developed parameters, i.e., recommended range of input linear energy of 0.25-0.4 J/mm; track width based on strut diameter, input linear energy and the orientation of strut; the overlap of the laser contour tracks of 35% and inside-out direction; it is possible to produce lattice structures with high material density (more than 99.8%) and low surface roughness in a wide range of strut diameters from 0.6 to 3 mm. The differences in lattice structure production of vertical and inclined struts are described and discussed in relation to the SLM process during powder melting with use of thermal transient simulation.

Selective laser melting (SLM) is an additive manufacturing technology suitable for producing cellular lattice structures using fine metal powder and a laser beam. However, the shape and dimensional deviations occur on the thin struts during manufacturing, influencing the mechanical properties of the structure. There are attempts in the literature to describe the actual shape of the struts’ geometry, however, on a smaller data sample only, and there is a lack of a universal FEA material model applicable to a wider range of lattice structure diameters. To describe the actual dimensions of the struts, a set of lattice structures, with diameters ranging from 0.6 to 3.0 mm, were manufactured using SLM. These samples were digitized using micro-computed tomography (CT) and fully analyzed for shape and dimensions. The results show large deviations in diameters of inscribed and circumscribed cylinders, indicating an elliptical shape of the struts. With increasing lattice structure diameter, the deviations decreased. In terms of the effect of the shape and dimensions on the mechanical properties, the Gaussian cylinder was found to describe struts in the diameter range of 1.5 to 3.0 mm sufficiently well. For smaller diameters, it is appropriate to represent the actual cross-section by an ellipse. The use of substitute ellipses, in combination with the compression test results, has resulted in FEA material model that can be used for the 0.6 to 3.0 mm struts’ diameter range. The model has fixed Young’s and tangential modules for these diameters and is controlled only by the yield strength parameter (YST).

Selective laser melting (SLM) is an additive manufacturing technology suitable for producing cellular lattice structures using fine metal powder and a laser beam. However, the shape and dimensional deviations occur on the thin struts during manufacturing, influencing the mechanical properties of the structure. There are attempts in the literature to describe the actual shape of the struts’ geometry, however, on a smaller data sample only, and there is a lack of a universal FEA material model applicable to a wider range of lattice structure diameters. To describe the actual dimensions of the struts, a set of lattice structures, with diameters ranging from 0.6 to 3.0 mm, were manufactured using SLM. These samples were digitized using micro-computed tomography (CT) and fully analyzed for shape and dimensions. The results show large deviations in diameters of inscribed and circumscribed cylinders, indicating an elliptical shape of the struts. With increasing lattice structure diameter, the deviations decreased. In terms of the effect of the shape and dimensions on the mechanical properties, the Gaussian cylinder was found to describe struts in the diameter range of 1.5 to 3.0 mm sufficiently well. For smaller diameters, it is appropriate to represent the actual cross-section by an ellipse. The use of substitute ellipses, in combination with the compression test results, has resulted in FEA material model that can be used for the 0.6 to 3.0 mm struts’ diameter range. The model has fixed Young’s and tangential modules for these diameters and is controlled only by the yield strength parameter (YST).

Selective laser melting (SLM) is an additive manufacturing technology suitable for producing cellular lattice structures using fine metal powder and a laser beam. However, the shape and dimensional deviations occur on the thin struts during manufacturing, influencing the mechanical properties of the structure. There are attempts in the literature to describe the actual shape of the struts’ geometry, however, on a smaller data sample only, and there is a lack of a universal FEA material model applicable to a wider range of lattice structure diameters. To describe the actual dimensions of the struts, a set of lattice structures, with diameters ranging from 0.6 to 3.0 mm, were manufactured using SLM. These samples were digitized using micro-computed tomography (CT) and fully analyzed for shape and dimensions. The results show large deviations in diameters of inscribed and circumscribed cylinders, indicating an elliptical shape of the struts. With increasing lattice structure diameter, the deviations decreased. In terms of the effect of the shape and dimensions on the mechanical properties, the Gaussian cylinder was found to describe struts in the diameter range of 1.5 to 3.0 mm sufficiently well. For smaller diameters, it is appropriate to represent the actual cross-section by an ellipse. The use of substitute ellipses, in combination with the compression test results, has resulted in FEA material model that can be used for the 0.6 to 3.0 mm struts’ diameter range. The model has fixed Young’s and tangential modules for these diameters and is controlled only by the yield strength parameter (YST).

Selective laser melting (SLM) is an additive manufacturing technology suitable for producing cellular lattice structures using fine metal powder and a laser beam. However, the shape and dimensional deviations occur on the thin struts during manufacturing, influencing the mechanical properties of the structure. There are attempts in the literature to describe the actual shape of the struts’ geometry, however, on a smaller data sample only, and there is a lack of a universal FEA material model applicable to a wider range of lattice structure diameters. To describe the actual dimensions of the struts, a set of lattice structures, with diameters ranging from 0.6 to 3.0 mm, were manufactured using SLM. These samples were digitized using micro-computed tomography (CT) and fully analyzed for shape and dimensions. The results show large deviations in diameters of inscribed and circumscribed cylinders, indicating an elliptical shape of the struts. With increasing lattice structure diameter, the deviations decreased. In terms of the effect of the shape and dimensions on the mechanical properties, the Gaussian cylinder was found to describe struts in the diameter range of 1.5 to 3.0 mm sufficiently well. For smaller diameters, it is appropriate to represent the actual cross-section by an ellipse. The use of substitute ellipses, in combination with the compression test results, has resulted in FEA material model that can be used for the 0.6 to 3.0 mm struts’ diameter range. The model has fixed Young’s and tangential modules for these diameters and is controlled only by the yield strength parameter (YST).

This paper deals with the research of the Selective Laser Melting (SLM) scanning strategy to produce lattice structures from AlSi10Mg powder material. Nowadays, most of the SLM end-users use the laser strategy and parameters recommended by powder or machine suppliers to produce different components. However, this setup can cause material and shape imperfection, especially in the case of low-volume lattice structures. In this study, the default meander scanning strategy for AlSi10Mg material was changed to contour strategy and its main SLM process parameters were developed. Commonly used experiments were modified to consider the lattice structure's shape and dimension. The results showed that by using developed parameters, i.e., recommended range of input linear energy of 0.25-0.4 J/mm; track width based on strut diameter, input linear energy and the orientation of strut; the overlap of the laser contour tracks of 35% and inside-out direction; it is possible to produce lattice structures with high material density (more than 99.8%) and low surface roughness in a wide range of strut diameters from 0.6 to 3 mm. The differences in lattice structure production of vertical and inclined struts are described and discussed in relation to the SLM process during powder melting with use of thermal transient simulation.

Selective laser melting (SLM) is an additive manufacturing technology suitable for producing cellular lattice structures using fine metal powder and a laser beam. However, the shape and dimensional deviations occur on the thin struts during manufacturing, influencing the mechanical properties of the structure. There are attempts in the literature to describe the actual shape of the struts’ geometry, however, on a smaller data sample only, and there is a lack of a universal FEA material model applicable to a wider range of lattice structure diameters. To describe the actual dimensions of the struts, a set of lattice structures, with diameters ranging from 0.6 to 3.0 mm, were manufactured using SLM. These samples were digitized using micro-computed tomography (CT) and fully analyzed for shape and dimensions. The results show large deviations in diameters of inscribed and circumscribed cylinders, indicating an elliptical shape of the struts. With increasing lattice structure diameter, the deviations decreased. In terms of the effect of the shape and dimensions on the mechanical properties, the Gaussian cylinder was found to describe struts in the diameter range of 1.5 to 3.0 mm sufficiently well. For smaller diameters, it is appropriate to represent the actual cross-section by an ellipse. The use of substitute ellipses, in combination with the compression test results, has resulted in FEA material model that can be used for the 0.6 to 3.0 mm struts’ diameter range. The model has fixed Young’s and tangential modules for these diameters and is controlled only by the yield strength parameter (YST).

This paper deals with the research of the Selective Laser Melting (SLM) scanning strategy to produce lattice structures from AlSi10Mg powder material. Nowadays, most of the SLM end-users use the laser strategy and parameters recommended by powder or machine suppliers to produce different components. However, this setup can cause material and shape imperfection, especially in the case of low-volume lattice structures. In this study, the default meander scanning strategy for AlSi10Mg material was changed to contour strategy and its main SLM process parameters were developed. Commonly used experiments were modified to consider the lattice structure's shape and dimension. The results showed that by using developed parameters, i.e., recommended range of input linear energy of 0.25-0.4 J/mm; track width based on strut diameter, input linear energy and the orientation of strut; the overlap of the laser contour tracks of 35% and inside-out direction; it is possible to produce lattice structures with high material density (more than 99.8%) and low surface roughness in a wide range of strut diameters from 0.6 to 3 mm. The differences in lattice structure production of vertical and inclined struts are described and discussed in relation to the SLM process during powder melting with use of thermal transient simulation.

Selective laser melting (SLM) is an additive manufacturing technology suitable for producing cellular lattice structures using fine metal powder and a laser beam. However, the shape and dimensional deviations occur on the thin struts during manufacturing, influencing the mechanical properties of the structure. There are attempts in the literature to describe the actual shape of the struts’ geometry, however, on a smaller data sample only, and there is a lack of a universal FEA material model applicable to a wider range of lattice structure diameters. To describe the actual dimensions of the struts, a set of lattice structures, with diameters ranging from 0.6 to 3.0 mm, were manufactured using SLM. These samples were digitized using micro-computed tomography (CT) and fully analyzed for shape and dimensions. The results show large deviations in diameters of inscribed and circumscribed cylinders, indicating an elliptical shape of the struts. With increasing lattice structure diameter, the deviations decreased. In terms of the effect of the shape and dimensions on the mechanical properties, the Gaussian cylinder was found to describe struts in the diameter range of 1.5 to 3.0 mm sufficiently well. For smaller diameters, it is appropriate to represent the actual cross-section by an ellipse. The use of substitute ellipses, in combination with the compression test results, has resulted in FEA material model that can be used for the 0.6 to 3.0 mm struts’ diameter range. The model has fixed Young’s and tangential modules for these diameters and is controlled only by the yield strength parameter (YST).

This paper deals with the research of the Selective Laser Melting (SLM) scanning strategy to produce lattice structures from AlSi10Mg powder material. Nowadays, most of the SLM end-users use the laser strategy and parameters recommended by powder or machine suppliers to produce different components. However, this setup can cause material and shape imperfection, especially in the case of low-volume lattice structures. In this study, the default meander scanning strategy for AlSi10Mg material was changed to contour strategy and its main SLM process parameters were developed. Commonly used experiments were modified to consider the lattice structure's shape and dimension. The results showed that by using developed parameters, i.e., recommended range of input linear energy of 0.25-0.4 J/mm; track width based on strut diameter, input linear energy and the orientation of strut; the overlap of the laser contour tracks of 35% and inside-out direction; it is possible to produce lattice structures with high material density (more than 99.8%) and low surface roughness in a wide range of strut diameters from 0.6 to 3 mm. The differences in lattice structure production of vertical and inclined struts are described and discussed in relation to the SLM process during powder melting with use of thermal transient simulation.

Themain drawback of laser powder bed fusion (L-PBF), commonly called selective lasermelting (SLM) is the high porosity which may lead to an early failure of the parts. To minimize it, the L-PBF parameters need to be optimized focusing on the laser power, scanning speed and hatching space. However, no standard guideline exists. In this study, an efficient and cost-effective methodology is developed and validated on AlSi12. This innovative methodology brings together single scan tracks (SST),macroscopic properties analysis and design of experiments (DOE). It requires three batches of SST, cubes and tensile samples. The DOE significantly decreases the manufacturing and characterization costs. 9 SST are sufficient to identify a process window that is 85% similar to the one obtained froma full factorial designwith 105 SST. This process windowreliably leads to high densities and better mechanical properties in comparison to the state-of-the-art properties reported in the literature for L-PBF AlSi12. In conclusion, a methodology using only 9 SST, 18 cubes and 12 tensile tests has been validated on AlSi12. It is further envisioned to optimize the L-PBF parameters of any existing or new alloy leading potentially towards better mechanical properties than the state-of-the-art in the literature.

An AlSi11Cu alloy was obtained by additive manufacturing (AM) using powder bed fusion by selective laser melting (SLM) from powders with a mean particle size of 40 µm. The printed alloy presented abnormal melting pools (MPs) sizes distribution described by a double fit of a normal logarithmic function that allowed the identification of two groups of melting pools with mean values of 150 µm and 320 µm. The mechanical properties indicated yield strengths between 370 MPa and 390 MPa, depending on the measurement direction. The radial direction showed the best strength and ductility while the transverse direction the worst behavior. Digital image correlation (DIC) analyzes demonstrated multiple strain concentration points in the tensile specimens and more significant strain acceleration for the longitudinal than the radial direction. The alloy's microstructure indicated the formation of columnar grains surrounded by small equiaxed grains describing an abnormal grain growth behavior. The material texture indicated a preferential orientation towards <001> ¿ to the building direction (BD), with the Cube and Goss texture components as the most intense. The abnormal behavior in the melting pools and the grain size allowed to observe that the largest grain growths were localized in the wider and deeper melting pools. The grain size abnormality and the preferred texture was also reflected in geometrically necessary dislocations (GNDs) density. The highest GNDs were found in the largest columnar grains, preferably oriented towards the <001> direction, while the lowest densities were grouped in the smaller equiaxed grains with random orientation. The radial direction's better mechanical response was due to higher numbers of plastic gradients' formation than in the longitudinal direction and the perpendicular orientation of the melting pools concerning the load direction. Therefore, radial oriented material fracture throughout the melting pools instead of the melting pool boundar, Peer Reviewed, Postprint (published version)

The field of orthopedic regenerative medical studies has begun to use porous metal structures for biomedical implants, which have lower strength and ingrowth behavior, similar to bones. It is possible to produce such porous metal structures with a designable microarchitecture or replicated topology by additive manufacturing. The main purpose of using these artificial pore geometries in the biomedical field is to increase the biocompatibility of the product by imitating the bone. In this study, bone samples from the femoral and vertebral regions of a sheep were obtained and scanned by microfocus computed tomography (Micro-CT). Trabecular bone models were produced from Ti6Al4V extralow interstitials powder using the selective laser melting with 1:1, 1:1.25, and 1:1.50 scales. The produced samples were scanned using Micro-CT, and 3D models were formed. The 3D models of the trabecular bone and samples were aligned in a computer environment to determine deviations in both size and angle of arms in the trabecular structure. It was found that the deviations decreased when the angle was above 60 degrees, whereas they significantly increased with the size below 150 microns. The size distribution and interconnectivity ratio of the pores formed in the production was obtained from the PNMs. It was determined that the mean equivalent diameters of vertebra and femoral pores, from the pore network models are 767 +/- 265 mu m and 623 +/- 245 mu m, and concluded that the samples produced in the scale of 1: 1 and 1: 1.25 could represent the pore size distribution in the bone., Gazi UniversityGazi University [06/2018-11]; Gulhane Medical Design and Production Center for modeling and production; EKTAM (Additive Manufacturing Technology Application and Research Center), This study is supported by Gazi University as a Scientific Research Project with number 06/2018-11. This study is supported by Gulhane Medical Design and Production Center for modeling and production. Authors thank EKTAM (Additive Manufacturing Technology Application and Research Center) for their support.

Laser powder bed fusion (PBF-LB/M) of metals belongs to the advanced additive manufacturing processes on the brink of industrialization. Successful manufacturing often requires the utilization of support structures to support overhangs, dissipate heat, and prevent distortion due to residual stresses. Since the support structures result in increased costs, research, as well as industry, aim at optimizing the application of those or the support structures themselves. New approaches are validated with individual use cases, though, preventing an objective comparison of optimization strategies. This paper contributes to the advance of support structure optimization by providing a benchmark strategy including part geometries, which enables to evaluate technical as well as economical aspects of support structures or support strategies. The benchmark process is demonstrated with the help of the currently most used block and pin support structures.

Dense oxide dispersion strengthened (ODS) 316 L steels with different amount of Y2O3 additions were successfully fabricated by selective laser melting (SLM) even though part of the added Y2O3 got lost during the process. The microstructure was characterized in details and the mechanical properties were tested at room temperature, 250 degrees C and 400 degrees C, respectively. The effect of the scanning speed on agglomeration of nanoparticles during SLM process was discussed. Superior properties, e.g., yield strength of 574 MPa and elongation of 91%, were achieved at room temperature in SLM ODS 316 L with additional 1% of Y2O3. At elevated temperatures, the strength kept high but the elongations dropped dramatically. It was observed that nano-voids nucleated throughout the whole gauge section at the sites where nanoinclusions located. The growth and coalescence of these voids were suppressed by the formation of an element segregation network before necking, which relieved local stress concentration and thus delayed necking. This unusual necking behavior was studied and compared to the previous theory. It appeared that the strong convection presented in the melt pool can evenly redistribute the short-time milled coarse Y2O3 precursor powder during SLM process. These findings can not only solve the problems encountered during the fabrication of ODS components but also replenish the strengthening mechanism of SLM 316 L thus pave a way for further improving of mechanical properties.

Additive manufacturing (AM) is an attractive way to shorten development time, reduce product weight and allow the manufacturing of more complex products than by conventional manufacturing processes. The problem arises when the previous traditional manufacturing requirements need to be fulfilled by AM as well as the volume production capability. This investigation is done together with Ericsson to evaluate the possibilities of the different AM technologies, post-processing methods and silver coating processes to guarantee the specifications of radiofrequency (RF) filters. Here, minimal RF signal insertion losses are targeted. Since insertion losses are dependent on surface roughness, surface smoothness is sought as well. Ericsson simulation software uses correction factors to account for surface roughness, however there are some inconsistencies between the simulated and actual surface roughness that is allowed in the parts. In AM parts, surface roughness is not easy to control since it depends on parameters related to feedstock, process and machine properties. Commonly, most AM components do not comply with requirements of lower surface roughness values. Therefore, parts need to be smoothened before silver plated; this step is necessary to ensure the electrical conductivity in this specific application. These finishing processes add costs to the final product and increase time to market. Firstly, a comprehensive study was carried out to better understand the landscape of AM technologies, postprocessing and silver coating methods. Secondly, the different processes are assessed with the help of selection matrices, considering the products requirements. The components to print are two RF filters with different shapes and dimensions but similar requirements. The CAD design is modified depending on each AM process and directly affects the results. Afterwards, the design of an experimental plan is carried out; the number of samples of each part comparing AM technologies, f

Additive Manufacturing (AM), especially Selective Laser Melting (SLM) enables the fabrication of complex and customized metal parts. However, 35 - 40 % of the manufacturing costs are required for manual post-processing steps. In order to reduce the cost of extensive post-processing, the process chain for AM parts must to be automated. In this respect, the robotic gripping and handling for the efficient clamping and machining is regarded as a key challenge. This work introduces bolts as a new universal interface for handling and clamping for the mass customization of AM parts. The SLM manufactured bolts are integrated in the part design and manufactured in the same AM process. The bolts can be easily removed after the machining process using a wrench. The application of the bolts is highlighted in two case studies. In this regard, the major contribution of this paper is the generated increased AM design freedom by adding universal clamping interfaces. The five side tool accessibility reduces the number of re-clamping. Finally no internal stress in the SLM part is induced by the clamping. This contributions further enable minimum lead time and mass customization for automated industrial series production.

In this study, the fatigue strength of 316 L stainless steel manufactured by selective laser melting (SLM) is evaluated. The effect of powder layer thickness and postmachining is investigated. Specimens were produced with 30 and 50 µm layer thickness and tested under high cycle fatigue in as-printed and postmachined conditions. Examination of the specimens reveals that in the as-printed condition, fatigue strength suffers from high roughness and surface tensile residual stresses as well as defects such as pores and lack of fusion voids. After machining, the fatigue strength was improved due to lower surface roughness, presence of compressive residual stresses, and removal of surface porosity. The results show that increasing the layer thickness (within the range tested) has a minor negative impact on fatigue strength; however, it has a major positive impact on the productivity of the SLM process. In addition, it is clear that the impact of postmachining on fatigue is far greater than that of the layer thickness. © 2020, The Author(s)., Funding details: 2015-03457; Funding text 1: Open access funding provided by RISE Research Institutes of Sweden. This work was supported by Sweden’s Innovation Agency [Grant Number: 2015-03457]. Ms. Anna Larsson and Mr. Heike Henrich from Höganäs AB are acknowledged for performing porosity and metallography analyses.

Ishimoto T., Wu S., Ito Y., et al. Crystallographic orientation control of 316L austenitic stainless steel via selective laser melting. ISIJ International, 60, 8, 1758. https://doi.org/10.2355/isijinternational.ISIJINT-2019-744., In recent years, additive manufacturing has attracted attention as a technology that enables control of the crystallographic texture of metallic materials. We achieved successful control of the crystallographic texture of 316L austenitic stainless steel using selective laser melting (SLM). Three distinguished textures were achieved by changing the laser scan speed, namely: the single crystalline-like texture with {001} orientation in the build direction, the crystallographic lamellar texture in which two kinds of grains with {011} and {001} orientations in the build direction are alternately stacked, and polycrystalline with relatively random orientation. The melt pool shape and the solidification behavior (thermal gradient and migration velocity of solid/liquid interface) in a melt pool could be important controlling factors for the evolution of the crystallographic texture under the SLM process.

Among metal additive manufacturing technologies, powder-bed fusion features very thin layers and rapid solidification rates, leading to long build jobs and a highly localized process. Many efforts are being devoted to accelerate simulation times for practical industrial applications. The new approach suggested here, the virtual domain approximation, is a physics-based rationale for spatial reduction of the domain in the thermal finite-element analysis at the part scale. Computational experiments address, among others, validation against a large physical experiment of 17.5[cm3]of deposited volume in 647 layers. For fast and automatic parameter estimation at such level of complexity, a high-performance computing framework is employed. It couples FEMPAR-AM,a specialized parallel finite-element software, with Dakota, for the parametric exploration. Compared to previous state-of-the-art, this formulation provides higher accuracy at the same computational cost. This sets the path to a fully virtualized model, considering an upwards-moving domain covering the last printed layers., Peer Reviewed, Postprint (author's final draft)

Additive manufacturing of a high-entropy alloy, AlCoCrFeNi, was studied with selective laser melting from gas atomized powder. A wide process parameter window in the SLM process was investigated but it was impossible to produce crack-free samples, attributed to stresses that originate during the building processes. The microstructure and elemental segregation in the SLM samples were compared with induction-melted AlCoCrFeNi. The induction-melted sample crystallizes in randomly oriented large grains (several hundred microns). Dendritic and inter-dendritic areas with slightly different chemical composition can be observed. Within these areas a spinodal decomposition occurs with a separation into FeCr- and NiAl-rich domains. Further spinodal decomposition within the FeCr-rich regions into Cr- and Fe-rich domains was observed by atom probe tomography. In contrast, the SLM-samples crystallizes in much smaller grains (less than 20 μm) with a dendrite-like substructure. These dendrite-like features exhibit distinct chemical fluctuations on the nm-scale. During annealing more pronounced chemical fluctuations and the formation of Cr-rich and Cr-poor regions can be observed. The difference in microstructure and spinodal decomposition between the induction-melted and SLM samples is attributed to the significantly higher cooling rate for SLM. This study shows that, by using different synthesis pathways, it is possible to modify the microstructure and segregation of element within alloys. This can be used to tune the materials properties, if the cracking behavior is handled e.g. by change of alloy composition to minimize phase transformations or use of a heating stage.

Selective Laser Melting (SLM) was used to process a powder mixture of CP Ti, 6.5 wt% Mo and 3.5 wt% Mo2C. The process parameters were optimized to obtain full-density, crack free parts. After the in situ decomposition of Mo2C in favor of the formation of TiC, the material consisted of a homogeneous dispersion of submicrometer sized TiC platelets in a β-(Ti,Mo) matrix exhibiting a high hardness up to 550 HV and compressive yield stress of 1164 ± 37 MPa. The microstructure and mechanical properties could be tailored by variation of the process parameters within the high-density processing window, as well as through post-process heat treatments., QC 20190626

Metal parts produced with the Selective Laser Melting (SLM) method have a great variety of uses today and because of this the requirements on the surface quality differ between applications. The surface treatments of the printed metal pieces, like other finishing phases, are often still manually worked on and thus are very time-consuming processes. This study focuses on the SLM printed AlSi10Mg aluminium specimen’s surface laser heat treatment with disk laser equipment (wavelength of 1030nm). The goal of this study was to achieve the desired effect on the aluminium’s surface quality with robotized laser heat treatment equipment. This was to show that the used finishing treatment method could be automated or robotized. The study showed that with the correct laser parameters, it is possible to generate desired effects and features on to the AlSi10Mg aluminium piece’s surface with a robotized process.

© 2014 The Authors. Published by Elsevier B.V. Selective Laser Melting (SLM) is an additive layer manufacturing technology that offers several advantages compared to conventional methods of production such as an increased freedom of design and a toolless production suited for variable lot sizes. Despite these attractive aspects today's state of the art SLM machines lack a holistic process monitoring system that detects and records typical defects during production. A novel sensor concept based on the low coherence interferometry (LCI) was integrated into an SLM production setup. The sensor is mounted coaxially to the processing laser beam and is capable of sampling distances along the optical axis. Measurements during and between the processing of powder layers can reveal crucial topology information which is closely related to the final part quality. The overall potential of the sensor in terms of quality assurance and process control is being discussed. Furthermore fundamental experiments were performed to derive the performance of the system.

Selective laser melting (SLM) is an additive manufacturing process, forming the desired geometry by selective layer fusion of powder material. Unlike conventional manufacturing processes, highly complex parts can be manufactured with high accuracy and little post processing. Currently, different steel, aluminium, titanium and nickel-based alloys have been successfully processed; however, high strength aluminium alloy EN AW 7075 has not been processed with satisfying quality. The main focus of the investigation is to develop the SLM process for the wide used aluminium alloy EN AW 7075. Before process development, the gas-atomized powder material was characterized in terms of statistical distribution: size and shape. A wide range of process parameters were selected to optimize the process in terms of optimum volume density. The investigations resulted in a relative density of over 99%. However, all laser-melted parts exhibit hot cracks which typically appear in aluminium alloy EN AW 7075 during the welding process. Furthermore the influence of processing parameters on the chemical composition of the selected alloy was determined.

Base plate preheating is one of the recent enhancing tools added to the process of Selective Laser Melting (SLM). This tool aims at a reduction of thermal stresses in SLM parts, achieved by decreasing the thermal gradients during SLM processing. In the current study, base plate preheating up to a temperature of 400°C is applied during SLM of 4 different materials, including aluminum 7075 alloy, nickel alloy Hastelloy X, H13 tool steel and CoCr. General trends, as well as material specific effects are discussed regarding part density, crack formation, internal stresses, microstructure and mechanical properties. These show how base plate preheating can induce different influences according to each particular material category., QC 20190826

This paper deals with the selective laser melting (SLM) processing strategy for strut-lattice structure production which uses only contour lines and allows the porosity and roughness level to be managed based on ombination of the input and linear energy parameters.

This paper deals with the selective laser melting (SLM) processing strategy for strut-lattice structure production which uses only contour lines and allows the porosity and roughness level to be managed based on ombination of the input and linear energy parameters.

This paper deals with the selective laser melting (SLM) processing strategy for strut-lattice structure production which uses only contour lines and allows the porosity and roughness level to be managed based on ombination of the input and linear energy parameters.

This paper deals with the selective laser melting (SLM) processing strategy for strut-lattice structure production which uses only contour lines and allows the porosity and roughness level to be managed based on ombination of the input and linear energy parameters.

This paper deals with the selective laser melting (SLM) processing strategy for strut-lattice structure production which uses only contour lines and allows the porosity and roughness level to be managed based on ombination of the input and linear energy parameters.

This paper deals with the selective laser melting (SLM) processing strategy for strut-lattice structure production which uses only contour lines and allows the porosity and roughness level to be managed based on ombination of the input and linear energy parameters.

Selective laser melting (SLM) is increasingly used in the industrial production of metallic parts. This creates the need for an efficient and accurate quotation costing. The manufacturing costs of a part mainly result from the machine running time for coating and exposure. At the time of the offer calculation the final orientation of the part in the build chamber and the composition of the build job are typically not known. Addressing this need, this paper presents and evaluates different statistical based methods for an automated and self-learning calculation for SLM given a part’s CAD data.

Selective laser melting is an additive manufacturing technology capable of creating near-net-shape products using a variety of materials. Parts made by selective laser melting have shortcomings in material behavior such as anisotropy, residual stresses, low ductility, and low fatigue limit. Such behavior is largely a result of the columnar grain structure found within the printed part. Fundamentally, the highly directional thermal gradient involved in the selective laser melting process, hampers the nucleation and promotes growth in one direction, and likely responsible for the observed columnar structure. The current study aims to modify such unfavorable nucleation conditions by introducing ultrasonic excitation into the selective laser melting process. The experiment was conducted on multiple layers of 304 L austenitic stainless steel as a model material on a specially built selective laser melting platform. Ultrasonic excitation has clearly shown to have an effect on as-printed microstructure leading to more desirable grain structure with a 46 to 54% decrease in aspect ratio as a result of the change in nucleation conditions. The results of this study suggest that ultrasonic excitation is a viable means to altering the selective laser melting grain structure. Moreover, it is highly likely that further optimization, and possibly a certain level of control on the resulting microstructure, can be achieved with the ultrasonic parameters. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

This study focusses on exploring the mechanical properties and machinability characteristics of Selective Laser Melted titanium alloy Ti-6Al-4V. It provides insights on how machining and additive manufacturing can be used collaboratively to improve the productivity and product quality of end titanium components.

In this work a finite-element framework for the numerical simulation of the heat transfer analysis of additive manufacturing processes by powder-bed technologies, such as Selective Laser Melting, is presented. These kind of technologies allow for a layer-by-layer metal deposition process to cost-effectively create, directly from a CAD model, complex functional parts such as turbine blades, fuel injectors, heat exchangers, medical implants, among others. The numerical model proposed accounts for different heat dissipation mechanisms through the surrounding environment and is supplemented by a finite-element activation strategy, based on the born-dead elements technique, to follow the growth of the geometry driven by the metal deposition process, in such a way that the same scanning pattern sent to the numerical control system of the AM machine is used. An experimental campaign has been carried out at the Monash Centre for Additive Manufacturing using an EOSINT-M280 machine where it was possible to fabricate different benchmark geometries, as well as to record the temperature measurements at different thermocouple locations. The experiment consisted in the simultaneous printing of two walls with a total deposition volume of 107 cm3 in 992 layers and about 33,500 s build time. A large number of numerical simulations have been carried out to calibrate the thermal FE framework in terms of the thermophysical properties of both solid and powder materials and suitable boundary conditions. Furthermore, the large size of the experiment motivated the investigation of two different model reduction strategies: exclusion of the powder-bed from the computational domain and simplified scanning strategies. All these methods are analysed in terms of accuracy, computational effort and suitable applications., Peer Reviewed, Postprint (author's final draft)

Selective laser melting (SLM) is an additive manufacturing process, forming the desired geometry by selective layer fusion of powder material. Unlike conventional manufacturing processes, highly complex parts can be manufactured with high accuracy and little post processing. Currently, different steel, aluminium, titanium and nickel-based alloys have been successfully processed; however, high strength aluminium alloy EN AW 7075 has not been processed with satisfying quality. The main focus of the investigation is to develop the SLM process for the wide used aluminium alloy EN AW 7075. Before process development, the gas-atomized powder material was characterized in terms of statistical distribution: size and shape. A wide range of process parameters were selected to optimize the process in terms of optimum volume density. The investigations resulted in a relative density of over 99%. However, all laser-melted parts exhibit hot cracks which typically appear in aluminium alloy EN AW 7075 during the welding process. Furthermore the influence of processing parameters on the chemical composition of the selected alloy was determined.

Selective Laser Melting (SLM) is a 3D-printing method to produce metal parts. In SLM a part is manufactured layer-by-layer by selectively melting a metal powder with a laser. Although SLM is a promising process for the production of high-quality parts, the implementation in high-tech industry is held back by a few barriers. One of the main barriers in the adoption of the process as a new production method are the high residual stresses and large deformations that arise in a part during manufacturing. The residual stresses may limit the load resistance and contribute to the formation of thermal cracks. Furthermore, it is difficult to ensure a constant quality during the build-process, resulting in e.g. varying porosity throughout the part. To obtain a better understanding of the process and predict processing and structural part characteristics prior to production, various modelling techniques have been proposed in literature. The majority of these models attempt to capture the movement of the laser by means of the finite element method (FEM). However, the fine discretization required to capture the steep thermal gradients in the vicinity of the moving laser spot, renders these types of models computationally too expensive to perform a full build-analysis of a component. Moreover, the transient nature of the heat transfer problem also increases the computational requirements. The aim of this research is to develop an efficient and simple, yet reasonably accurate thermal model of the SLM process, that is able to describe the influence of the process parameters on the level of residual stresses and the amount of porosity. To reach this objective, a semi-analytical modelling approach is proposed. The moving laser is represented with a set of point sources for which the closed form analytical solution is known. This solution efficiently captures the transient nature of the heat transfer problem and the steep thermal gradients in the vicinity of the moving laser. Since an, Engineering Mechanics, Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering

Selective Laser Melting (SLM) is an Additive Manufacturing (AM) technique that uses a laser to selectively melt metallic powder in a layer-wise manner, in order to produce functional metal components. It offers great freedom in design and facilitates fast iterations, with the potential of speeding up development phases throughout a wide range of industries. Despite these opportunities, its application into industry is limited. One of the problems that is a limiting factor, is the high residual stress and large deformations that are introduced to the components during manufacturing. This is detrimental to the fatigue strength of a part and can even lead to cracks. In order to be able to understand, predict and eventually prevent such phenomena, a wide range of numerical models is already available in literature. Each of these models focus at one of more specific aspects of the SLM process. However an accurate prediction of the residual stresses for a complete component, requires detailed knowledge on the thermal history throughout the component. Due to a moving heat source, this problem is transient by nature and due to the local heat input by the laser, steep temperature gradients arise. This requires a fine discretisation, resulting in a computationally expensive model. The goal of this thesis is to contribute to the development of a computationally efficient process model of SLM, by developing a computationally efficient and reasonably accurate model of the thermal evolution of a part manufactured with the SLM process. In this work, two different modelling approaches are investigated, both use the Finite Difference (FD) method to discretise the problem at hand. The first approach uses thermal modes, which is the application of a modal solution to the heat equation. This method aims to use a truncated number of superposed eigensolutions and thereby reduce the computational load. Numerical eigenvalues and eigenvectors (also called thermal modes), were obtained for a, Mechanical, Maritime and Materials Engineering, Precision and Microsystems Engineering, Engineering Mechanics

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Titanium implants prepared by selective laser melting (SLM), a method of additive manufacturing, were subjected to implantation in beagle dogs for two and four weeks. Argon ion beam-polished cross sections of the implants after in vivo tests were characterized by scanning electron microscope (SEM) to evaluate the bone–implant interface and the early peri-implant biomineralization with sufficiently improved resolution. Two bone mineralization mechanisms were disclosed. As early as two weeks after implantation, a layer of new bone was found to form directly on the implant surface and bone in-growth was also observed. Osseointegration was found to establish partly at the tip of the implants. After healing for four weeks it was found that osseointegration was established around the entire tip of the implants, whereas only partly at the third thread region of the implants. The experimental evidences observed reveal that an inherent highly porous surface of the titanium implants generated by selective laser melting is favorable for new bone apposition.

Unique crystal textures formed by selective laser melting of a CoCrMo alloy were characterized by electron backscattered diffraction. Preferred crystallographic orientations were found for individual grains in the solid alloy microstructure. Along the building or radial grain growth direction in the rapidly cooling melt pool the formed columnar grains were not purely < 001 > or < 111 >, as reported before, but a concurrence of < 001 > and < 011 >. Along the scanning direction, a (011) < 100 > texture was limited to the outmost surface whereas in the solid bulk the preferred orientation was a < 001 > fiber texture., AuthorCount:7

Nowadays the dynamics of markets, technology advances, and companies’ competition have brought changes in metal processing. Recent technical improvements of additive manufacturing (AM) processes have shifted their application from prototyping to the production of end-use parts either as customised or series. The extended geometric flexibility, coupled with the reduced time of production and the improved efficiency in resources utilization inherent of Selective laser melting (SLM) are the characteristics sought by aircraft industry in order to develop and progress. This thesis aims to contribute to the study and analysis of the new strategy of production Selective Laser Melting in the manufacture of metallic components for aeronautical use. Specifically the mechanical characterization of the titanium alloy Ti6Al4V is performed. For this purpose several samples and specimens were manufactured in the SLM equipment at Centre for Rapid and Sustainable Product Development (CDRSP) and the mechanical tests were carried out at the Instituto Superior Técnico (IST) for further analysis of the results. SLM is an additive manufacturing technique through which components are built by selectively melting powder layers using a focused laser beam. With the proper setting of the SLM process, a relative density above the required value in the aircraft industry (above 99%) is achieved. Specifically in this work, relative densities of around 99.6% were achieved. However the process is characterized by short laser-powder interaction times and localized high heat input, which leads to steep thermal gradients, rapid solidification and fast cooling resulting in a specific microstructure. In order to obtain optimal mechanical properties, heat treatments are necessary due to the original martensitic microstructure. Moreover finishing mechanical process is required, firstly due to the need of remove the parts from the platform and secondly to decrease the surface roughness of the parts.

Zhang, L. C., & Liu, Y. (2019). Additive manufacturing of titanium alloys for biomedical applications. In B. AlMangour (Ed.), Additive manufacturing of emerging materials (pp. 179-196). Springer, Cham. https://doi.org/10.1007/978-3-319-91713-9_5

Zhang, L. C., & Qin, P. (2019). Corrosion behaviors of additive manufactured titanium alloys. In In B. AlMangour (Ed.), Additive manufacturing of emerging materials (pp. 197-226). Springer, Cham. https://doi.org/10.1007/978-3-319-91713-9_6

Gu, X. H., Zhang, J. X., Fan, X. L., & Zhang, L. C. (2020). Corrosion Behavior of Selective Laser Melted AlSi10Mg Alloy in NaCl Solution and Its Dependence on Heat Treatment. Acta Metallurgica Sinica (English Letters), 33(3), 327-337. https://doi.org/10.1007/s40195-019-00903-5