Microstructure and properties of Ag/SnO2 functional material manufactured by selective laser melting
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Ag/SnO2, as a promising and environment-friendly electrical contact material, is widely applied in low-voltage apparatus. But the properties of Ag/SnO2 composites is difficult to improve due to the poor distribution phases and difficult component design. In this work, the Ag/SnO2 composites are prepared by selective laser melting. To get better performance, Ag/SnO2 composites with different energy density were studied. The microstructure was observed by field emission scanning electron microscope. In addition, reinforced SnO2 phase was characterized by X-ray diffraction and transmission electron microscope. The results indicated that the microstructure, relative density and hardness of are influenced by energy density, while Ag/SnO2 composites with homogeneous microstructure, high relative density, higher hardness and lower electrical resistivity can be obtained by proper energy density (E = 68 J/mm3).Keywords:
Selective Laser Melting
Relative density
Field emission microscopy
Selective Laser Melting (SLM) demonstrates the 21st century's manufacturing infrastructure in which powdered raw material is melted by a high energy focused laser, and built up layer-by-layer until it forms three-dimensional metal parts. SLM process involves a variation of process parameters which affects the final material properties. 316L stainless steel compacts through the manipulation of building orientation and powder layer thickness parameters were manufactured by SLM. The effect of the manipulated parameters on the relative density and dimensional accuracy of the 316L stainless steel compacts, which were in the as-build condition, were experimented and analysed. The relationship between the microstructures and the physical properties of fabricated 316L stainless steel compacts was investigated in this study. The results revealed that 90° building orientation has higher relative density and dimensional accuracy than 0° building orientation. Building orientation was found to give more significant effect in terms of dimensional accuracy, and relative density of SLM compacts compare to build layer thickness. Nevertheless, the existence of large number and sizes of pores greatly influences the low performances of the density.
Selective Laser Melting
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Selective laser melting (SLMing) is a new advanced material processing technology which is used in fabricating parts with complex shape. Hot isostatic pressing (HIPing) is a manufacture technology which forms parts by imposing high heat and pressure on metal powders or semi-manufactured parts. Considering the advantages of both the technologies, they can be combined to produce higher-quality parts free from the limitation of the shape of parts. AISI316L stainless steel is widely used in manufacturing varies of complex metal parts. In this research, three AISI316L stainless steel samples with different relative densities were acquired by controlling the fabricating parameters in SLM. The SEM and optical microscopy analysis were employed to characterize the relative density, microstructure, deformation by comparing the differences between SLM samples and SLM-HIPped samples. In addition, the influence of HIP process on microstructures of samples in different laser fabricating parameters was investigated by analyzing the mechanisms of SLM and HIP. The results show that HIP can close vacuum crack and pore, consequently, the relative density of SLM samples increases after HIP, making the property of the samples improved and microstructure better-distributed. Moreover, the increment of relative density under the same HIP condition is also discussed.
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Hot isostatic pressing
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This work examined the behaviors of densification and microstructural formation of the Al–10 mass%Si–0.35 mass%Mg alloy fabricated by Selective Laser Melting (SLM) method on the basis of experimental work and machine learning. Additionally, the effect of scanning repeated twice in each layer (double scanning) in the SLM process was also investigated. The SLM-ed Al–10 mass%Si–0.35 mass%Mg alloy exhibited the columnar grained microstructure with a (α-Al–Si) eutectic cell structure. Refined microstructures were produced at an increasing scanning speed with a decreasing the energy density (J/mm3). Relative density tended to increase with an increasing of energy density for scan pitch conditions of 0.1 mm and 0.05 mm. And a scattering was obviously exhibited at a higher relative density more than 95%. The analysis based on machine learning revealed that a scanning pitch of 0.2 mm was just a condition to achieve a high relative density. Except for the condition at a scanning pitch of 0.2 mm, a scan speed was the most important factor in affecting the relative density. Thus, a machine learning approach enabled to identify the important processing factor for affecting the behavior quantitatively. Additionally, compared to a conventional single scanning process, it was found in this work that the double scanning resulted in a higher relative density with keeping the fine microstructural formation.
Selective Laser Melting
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Laser Scanning
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Porous metallic materials are materials that have closed cell or open cell pores within their microstructure. These materials have high stiffness-to-weight ratios and serve as good heat exchanging materials due to the high surface area. Selective Laser Melting (SLM) method of additive manufacturing (AM) can manufacture these materials to save more time and provides more intricate designs compared to traditional manufacturing. The aim of this study was to manufacture porous materials by controlling the processing parameters (laser power, scanning speed, layer thickness, and hatch spacing) that affect the energy density applied on the metal powder during the melting. Lower energy density applied in the laser melting process leads to higher porosity. The experiments were designed using an L9 orthogonal array through Taguchi's method to minimize the number of runs carried out. SLM Tool Steel 1.2709 specimens were manufactured with three levels of each processing parameters that contribute to a lower energy density compared to the standard energy density of 69.4 J/mm3. The relative density of each specimen was measured using Archimedes' methods and converted to Signal-to-Noise (S/N) Ratios. The S/N ratios were used to analyze the ranking of parameters to the effect of relative density through MINITAB. The ranking of parameters was confirmed by conducting Analysis of Variance (ANOVA) analysis with the S/N ratios and comparing the percentage contribution of each parameter towards the relative density of the specimens. Hatch spacing was found to have the most effect on the relative density the most followed by laser power, layer thickness and scanning speed. Regression analysis was conducted to obtain a regression equation for relative density in terms of the four SLM processing parameters. Confirmation tests will be conducted by fabricating porous specimens with the regression equation with a targeted relative density and measuring the relative density of the fabricated specimen.
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Orthogonal array
Power density
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Selective laser melting (SLM) process is the foremost metal additive manufacturing (AM) technology that precisely generates complex geometries from CAD files. Mechanical behavior of printed parts is greatly affected by printing parameters and defining the optimal values of the process parameters to enhance the mechanical properties of components is highly regarded. In this work, four different SLM parameters including scanning speed, laser power, hatch spacing and scan pattern angle were applied to manufacture SS316L parts. For investigating the effect of each parameter and their interactions on hardness and relative density, Taguchi L16 orthogonal array was employed. The influence of part geometry and remelting is also evaluated in order to optimize the hardness and relative density of components. The results exhibited that the laser scanning speed was the most predominant SLM parameter for investigated mechanical properties. Analyzing the regression formula obtained from the results showed that the optimum laser energy density resulted in a 0.37% and 5.38% increase compared to the lowest relative density and hardness, respectively. High remelting energy associated with low remelting scanning speed, caused an 8.5% and 17.9% rise in hardness of squares and triangles, respectively; however, it led 12.5% reduction in hardness for circles. Remelting caused a 2.32% reduction, 2.1% increase and 5.3% rise on relative density for circles, squares and triangles, respectively.
Selective Laser Melting
Relative density
Orthogonal array
Laser Scanning
Power density
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Nine variants of regular lattice structures with different relative densities have been designed and successfully manufactured. The produced structures have been subjected to geometrical quality control, and the manufacturability of the implemented selective laser melting (SLM) technique has been assessed. It was found that the dimensions of the produced lattice struts differ from those of the designed struts. These deviations depend on the strut orientation in relation to the specimen-building direction. Additionally, the microstructures and phase compositions of the obtained structures were characterized and compared with those of conventionally produced 316L stainless steel. The microstructure analysis and X-ray diffraction (XRD) patterns revealed a single austenite phase in the SLM samples. Both a certain broadening and a displacement of the austenite peaks were observed due to residual stresses and a crystallographic texture induced by the SLM process. Furthermore, the mechanical behavior of the lattice structure material has been defined. It was demonstrated that under both quasi-static and dynamic testing, lattice structures with high relative densities are stretch-dominated, whereas those with low relative densities are bending-dominated. Moreover, the linear dependency between the value of energy absorption and relative density under dynamic loading conditions has been established.
Selective Laser Melting
Relative density
Lattice (music)
Lattice constant
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Nine variants of regular lattice structures with different relative densities have been designed and successfully manufactured. The produced structures have been subjected to geometrical quality control, and the manufacturability of the implemented selective laser melting SLM technique has been assessed. It was found that the dimensions of the produced lattice struts differ from those of the designed struts. These deviations depend on the direction of geometrical evaluation. Additionally, the microstructures and phase compositions of the obtained structures were characterized and compared with those of conventionally produced 316L stainless steel. The microstructure analysis and X-Ray Diffraction XRD patterns revealed a single austenite phase in the SLM samples. Both a certain broadening and a displacement of the austenite peaks were observed due to residual stresses and a crystallographic texture induced by the SLM process. Furthermore, the mechanical behavior of the lattice structure material has been defined. It was demonstrated that under both quasi-static and dynamic testing, lattice structures with high relative densities are stretch-dominated, whereas those with low relative densities are bending-dominated. Moreover, the linear relationship between the energy absorption and relative density under dynamic loading conditions has been defined
Selective Laser Melting
Relative density
Lattice (music)
Lattice constant
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Selective Laser Melting SLM is one of the most popular three dimensional printing methods, which can be used for manufactured real elements (with high geometrical complexity) in many application, such as medicine, automotive or aerospace industries. The SLM final parts are characterized by high mechanical properties and satisfactory physicochemical properties. However, the properties of parts depend of process parameters optimization. In this paper, effects of processing parameters, such as laser power P, scanning speed SP, layer thickness t or point distance PD on defect formation and relative densities of manufactured elements are explored. For the purpose the stainless steel 316L and pure titanium Grade II are used. The process optimization were carried out according to the formula of energy density, which is delivered to the powder material. The stainless steel samples were divided into 12 groups, depends of the energy density. The titanium parts were printed at the same value of energy, and the process parameters are changed. The microscope observation and relative density measurements were carried out. Based on the obtained results, it can be confuted that the SLM parameters have a significant effect on the samples properties and the mechanism formed defect in both material are similar.
Selective Laser Melting
Relative density
Titanium alloy
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In this work, the influence of processing condition on relative density and mechanical properties of specimens prepared by Selective Laser Melting (SLM) technique using 18-Ni maraging steel powder was investigated. The results show that it is necessary to control laser energy density of about 65-80 J/mm^3 to obtain SLM specimens with relative density higher than 99.9%. In addition, it was confirmed that mechanical properties of dense SLM specimens were less influenced by building direction on the base plate.
Selective Laser Melting
Maraging steel
Relative density
Base (topology)
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Selective Laser Melting
Relative density
Power density
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