Search

Laser-based powder bed fusion of metals (PBF-LB/M) is a widely used additive manufacturing process characterized by a high degree of design freedom. As a result, near fully dense complex components can be produced in near-net shape by PBF-LB/M. Recently, the PBF-LB/M process was found to be a promising candidate to overcome challenges related to conventional machining of the Fe64Ni36 Invar alloy being well known for a low coefficient of thermal expansion (CTE). In this context, a correlation between process-induced porosity and the CTE was presumed in several studies. Therefore, the present study investigates whether the unique thermal properties of the PBF-LB/M-processed Fe64Ni36 Invar alloy can be tailored by the selective integration of defects. For this purpose, a full-factorial experimental design, representing by far the largest processing window in the literature, was considered, correlating the thermal expansion properties with porosity and hardness. Furthermore, the microstructure and mechanical properties were investigated by scanning electron microscopy and quasi-static tensile tests. Results by means of statistical analysis reveal that a systematic correlation between porosity and CTE properties could not be determined. However, by using specific process parameter combinations, the microstructure changed from a fine-grained fan-like structure to a coarse columnar structure. [ABSTRACT FROM AUTHOR]

The present study investigates the synergistic enhancement of hot corrosion resistance (900 °C, 75%Na2SO4+25%NaCl) and mechanical properties of IN738LC alloy prepared by selective laser melting after heat treatment. The results indicate that the M23C6 precipitation at the grain boundaries coupled with smaller-sized γ′ phase distribution in the inner grain is conducive to the formation of thicker Cr2O3 outer layer and Al2O3 inner layer for the samples, which effectively hinders the diffusion of S and Cl elements penetrate to the matrix, enhancing the hot corrosion resistance. Additionally, the presence of small-sized γ′ phase and re-crystallization-induced grain refinement contribute to an increase in yield strength (σYS = 1261 MPa) and ultimate tensile strength (σUTS = 1360 MPa) for the alloy.

The mechanical properties of 10Kh12N10Т and 08Kh18N9 stainless steel components in additive manufacturing are investigated. Selective laser melting (SLM) and wire arc additive manufacturing (WAAM) are considered. Components produced by selective laser melting are found to be stronger than those produced by wire arc additive manufacturing. Additional heat treatment reduces the strength but improves the plasticity, especially in wire arc additive manufacturing. The influence of structural porosity on the mechanical properties of the components is assessed. [ABSTRACT FROM AUTHOR]

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability. [ABSTRACT FROM AUTHOR]

The feasibility of manufacturing high-performance components with complex structures is limited due to cracks in some superalloys fabricated by selective laser melting (SLM). By controlling the main process parameters such as scanning strategy, the adverse effects of cracks can be effectively reduced. In this paper, the effects of two different SLM scanning strategies with island and 'back-and-forth' and post-heat treatment on the cracks and mechanical properties of selective-laser-melted (SLMed) K438 alloy were investigated. The results show that the SLM method of the 'back-and-forth' scanning strategy had better lap and interlayer rotation angles and a more uniform distribution of laser energy compared with the island scanning strategy. The residual stress accumulation was reduced and crack formation was inhibited under this scanning strategy owing to the cooling and shrinkage process. In addition, the dislocation motion was hindered by the formation of uniformly dispersed MC carbides and γ' phases during the SLM K438 alloy process, which resulted in the density of the as-built SLMed K438 alloy being up to 99.34%, the hardness up to 9.6 Gpa, and the tensile strength up to 1309 MPa. After post-heat treatment, the fine secondary γ' phases were precipitated and dispersed uniformly in the Ni matrix, which effectively improved the Young's modulus and tensile strength of the alloy by dispersing the stress-concentrated area. [ABSTRACT FROM AUTHOR]

Laser-based powder bed fusion of metals (PBF-LB/M) is a widely used additive manufacturing process characterized by a high degree of design freedom. As a result, near fully dense complex components can be produced in near-net shape by PBF-LB/M. Recently, the PBF-LB/M process was found to be a promising candidate to overcome challenges related to conventional machining of the Fe64Ni36 Invar alloy being well known for a low coefficient of thermal expansion (CTE). In this context, a correlation between process-induced porosity and the CTE was presumed in several studies. Therefore, the present study investigates whether the unique thermal properties of the PBF-LB/M-processed Fe64Ni36 Invar alloy can be tailored by the selective integration of defects. For this purpose, a full-factorial experimental design, representing by far the largest processing window in the literature, was considered, correlating the thermal expansion properties with porosity and hardness. Furthermore, the microstructure and mechanical properties were investigated by scanning electron microscopy and quasi-static tensile tests. Results by means of statistical analysis reveal that a systematic correlation between porosity and CTE properties could not be determined. However, by using specific process parameter combinations, the microstructure changed from a fine-grained fan-like structure to a coarse columnar structure.

This study focuses on the additive manufacturing technique of selective laser melting (SLM) to produce Ti-6Al-4V-Zn titanium alloy. The addition of zinc at 0.3 wt.% was investigated to improve the strength and ductility of SLM Ti-6Al-4V alloys. The microstructure and mechanical properties were analyzed using different vacuum heat treatment processes, with the 800-4-FC specimen exhibiting the most favorable overall mechanical properties. Additionally, zinc serves as a stabilizing element for the β phase, enhancing the resistance to particle erosion and corrosion impedance of Ti-6Al-4V-Zn alloy. Furthermore, the incorporation of trace amounts of Zn imparts improved impact toughness and stabilized high-temperature tensile mechanical properties to SLM Ti-6Al-4V-Zn alloy. The data obtained serve as valuable references for the application of SLM-64Ti. [ABSTRACT FROM AUTHOR]

Globally, SLM is changing the way organizations design and manufacture products. It is an emerging manufacturing technique. This technique is classified as additive layered manufacturing, as the component is built by adding material in layers. Components/parts manufactured by Selective Laser Melting (SLM) find a lot of applications in many industries like aerospace, biomedical and automobile. Proposed research work investigates the effect of various process parameters on the mechanical properties manufactured by the SLM process of Stainless Steel 316L [SS316L]. The literature indicates that process parameters having maximum impact on mechanical properties includes Laser Power (P), Exposure Time (T), Border Power (BP) and Hatch Spacing (HS). The effect of these process parameters on Ultimate Tensile Strength (UTS) and Surface Roughness (SR) was investigated. This research work aims to enhance the performance measures, by optimizing the process parameters used in SLM with Grasshopper Optimization Algorithm (GOA) technique. GOA was used to achieve maximum ultimate tensile strength and minimum surface roughness in a single set of experimentation through a multiobjective approach. [ABSTRACT FROM AUTHOR]

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability.

Selective laser melting (SLM) as an additive manufacturing (AM) technique shows great potential to produce complex and high-density three-dimensional structures at high speeds. Currently, alloy materials based on aluminum–silicon (AlSi), including AlSi7Mg and AlSi10Mg, are widely used in AM technology. However, the residual stress caused by rapid cooling was one of the critical issues affecting the tensile and yield strength, dimensional accuracy, and reliability of fabricated parts. In this study, we systematically investigated changes in the microstructure, residual stress, and mechanical properties of AlSi7Mg and AlSi10Mg materials after a heat treatment. The changes in electrical properties were also investigated. The heat treatment process reduced the residual stress of the materials. After the heat treatment, the silicon (Si) network structure and Si dissolved in the Al matrix were completely precipitated and existed as an independent fine spherical precipitate. The AlSi7Mg material has a weaker solid-solution hardening effect due to lower volume fraction of Si, resulting in lower tensile strength, lower hardness, and higher elongation than the AlSi10Mg material. After the heat treatment, the tensile and yield strength of both materials decreased, and the elongation increased. On the other hand, the electrical conductivity of the materials was improved after the heat treatment due to the Si which precipitated in the Al matrix, acting as an impurity. The electrical conductivity and mechanical properties of the AlSi alloy depend on the Si content of the materials. Therefore, the electrical and mechanical properties can be enhanced by optimizing the appropriate Si content in the material. [ABSTRACT FROM AUTHOR]

A significant correlation between scanning strategies and the quality of parts manufactured additively with Selective Laser Melting (SLM) technology is shown. Therefore, a in deep study of the influence of scanning strategy is of great value for the manufacturing process in order to promote SLM technology in applications with high service requirements. In particular, this research is carried out on 17-4PH stainless steel parts, which is an alloy widely used in sectors such as aerospace or automotive for its excellent mechanical properties. This research proposes to evaluate the properties of 17-4PH parts manufactured using three usual scanning strategies (normal, concentric and hexagonal) in order to optimize the SLM process depending on the final part application. According to the obtained results, the following general conclusions have been drawn. Hexagonal strategy can be considered the most appropriate in terms of porosity. Both hexagonal and normal strategy have good mechanical properties, as well as geometrical and dimensional quality. Regarding surface finish of top face (where the used scanning pattern is visible), normal strategy is the most appropriate. In general, concentric strategy presents different results from the others: larger and irregular pores, ductile tensile behaviour, low roughness on lateral faces, and high geometrical errors in samples with large scanning vectors. As a future work, it is proposed to manufacture SLM parts combining these strategies in order to improve their properties. In addition, it is proposed to evaluate the influence of different post-process operations on the quality of parts printed by SLM using different strategies.

An investigation of the failure process of maraging steel grade X3NiCoTi18-9-5 produced by the SLM method that is subjected to various three-dimensional stress-states has been carried out. In this paper, deformations and damage evolution are analysed experimentally and numerically. Three microstructures of the SLM steel were obtained after the appropriate heat treatment. Tensile tests of smooth specimens and axisymmetric notched specimens have been performed. Numerical models of the samples with ring notches were made in order to determine the stress state and displacement field in the notch area at the moment of the sample’s breakage as well as to compare the experimentally determined effective strain in the notch after the sample’s breakage with the deformation being calculated on the basis of the numerical solution. As a result of the research, it was found that the type of fracture of samples obtained from X3NiCoTi18-9-5 steel powder by the SLM method depends on the size of the ring notch’s radius. Based on the performed numerical calculations and experimental tests, it was found that, for each of the analysed variants of heat treatment, it was possible to indicate the approximate limit value of triaxiality factor Tf, above which there is a scrap of brittle X3NiCoTi18-9-5 steel produced by the SLM method. This value is determined by the characteristic bending of the function that determines the relationship between triaxiality factor Tf and effective strain eeff.

The optimal SLM conditions of 304L stainless steel were obtained by single factor and orthogonal tests. Results indicated that the optimal hardness (75 HRB) and Relative Density (RD 99.24%) could be obtained when the laser output power was 190 W, the scanning distance was 0.09 mm and the scanning speed was 800 mm/s. The microstructure of fish scales was uniform and compact with a few pores in the optimal sample. The fine particles were randomly distributed near the edge of the molten pool, and some preferred granular columnar crystal structures were formed. Abundant entanglement dislocations were observed between cell structures, forming dislocation clusters. Spherical nano-precipitates, rich in Si, Mn, and O, were also observed near cell structures. The mechanical properties of the specimens were highly anisotropic, and there were obvious necking and ductility at the tensile fracture. [ABSTRACT FROM AUTHOR]

Optimally designed bone implants with a suitable porous structure have similar mechanical properties to bone tissue and at the same time have good biocompatible and excellent bioactivity. The preparation of medical biological porous scaffolds by metal 3D printing technology is one of the most promising and attractive biomedical applications. The traditional regular porous and self-growing porous scaffolds were established by using CAD and C4D software, and the different scaffolds of three-dimensional models in similar porosity was obtained. A three-dimensional model of a scaffold with a porous structure was designed, and the porous scaffold was prepared by selective laser melting (SLM) technique, and its microstructure and mechanical properties were analysed. Under the similar porosity, the average hardness of the surface of the self-growing structure porous scaffold reached 236.5HV, and the stress at 5% compressive strain after heat treatment was close to 75 MPa. The original surface of the 316L porous scaffold made by SLM has the potential to effectively promote the differentiation of MG63 cells into osteoblasts. At the same time, the surface morphology and structure of the self-growth scaffold are similar to human cancellous bone, which is conducive to cell attachment and growth, so it is more suitable for repairing diseased parts of human bones.

316L porous skeletal scaffolds prepared by selective laser melting (SLM) technology are currently widely used in bone injuries. Its successful implantation is predicated on having properties that match those of natural bone. The process parameters significantly influence the performance of SLM-316L porous scaffold. In this study, the nine-group shaping process parameters were determined by orthogonal method. The 316L porous scaffolds were tested in compression, electrochemistry, XRD and microstructure. The influence of process parameters on the performance of body-centered cubic peripheral square structure bracket was investigated. The influence laws of process parameters on microstructure, mechanical properties and corrosion resistance were obtained. The results show that process parameters have a significant effect on the microstructure, properties and defect distribution. The reduction of defects and grain refinement in the stent is conducive to the improvement of compressive properties and hardness of the stent. The magnitude of the hardness is inversely related to the grain size. The corrosion current density of porous scaffolds are also affected by their microscopic defects and grain size. At an energy density of 78.70 J mm ^−3 presents the least defects and obtains smaller grains, resulting in the best mechanical properties and corrosion resistance.

This study focuses on the additive manufacturing technique of selective laser melting (SLM) to produce Ti-6Al-4V-Zn titanium alloy. The addition of zinc at 0.3 wt.% was investigated to improve the strength and ductility of SLM Ti-6Al-4V alloys. The microstructure and mechanical properties were analyzed using different vacuum heat treatment processes, with the 800-4-FC specimen exhibiting the most favorable overall mechanical properties. Additionally, zinc serves as a stabilizing element for the β phase, enhancing the resistance to particle erosion and corrosion impedance of Ti-6Al-4V-Zn alloy. Furthermore, the incorporation of trace amounts of Zn imparts improved impact toughness and stabilized high-temperature tensile mechanical properties to SLM Ti-6Al-4V-Zn alloy. The data obtained serve as valuable references for the application of SLM-64Ti.

To improve the performance of selective laser melted 316L stainless steel components the effects of laser power and heat treatment methods on the surface morphology and mechanical properties of the formed parts are studied. The research results show that with the increase of the laser power, the surface morphology quality and mechanical properties of the formed parts initially increase and then decrease. When the laser power is 170 W a formed part with better surface morphology and mechanical properties can be obtained. The grain size and elongation can be increased by heat treating the formed part. Among them, the air cooling method can obtain better mechanical properties than the water cooling method. The combination of laser power and heat treatment is a promising method to improve the performance of selected laser melted 316L stainless steel parts. [ABSTRACT FROM AUTHOR]

Abstract—This article presents the results of fatigue tests of smooth cylindrical specimens while controlling full deformation under conditions of symmetric cycle and higher temperature. The interaction between material fatigue properties has been considered with consideration for stresses, plastic deformation, and number of cycles before failure. The deformation curves plotted by experimental data are compared with the deformation curves plotted by estimating methods. [ABSTRACT FROM AUTHOR]

Metal Additive Manufacturing (AM) processes are developing quickly. These processes have several attractive qualities, however, the quality of manufactured parts still remains a major issue that needs to be addressed if it is to become a prevalent technology in the industry. In some powder bed fusion techniques, such as Selective Laser Melting (SLM), there is a portion of initial powder that does not melt and it can be recycled to ensure the economic and environmental viability of the process. In previous research, we demonstrated the morphological, chemical and microstructural change suffered by 17-4 PH stainless steel powder after reusing it in a SLM manufacturing process. In this work, the properties of 17-4 PH stainless steel parts, printed from powder in different recycling states (virgin powder (P0) and 20 times reused powder (P20)), were evaluated, in order to establish good recycling procedures and optimise the SLM process performance. Analyses of the properties revealed a slight decrease in roughness and pore size with powder recycling. The external porosity of the samples is similar in both powder states; however, internal porosity decreases by increasing the number of reuse cycles. Regarding the microstructural analysis, a slight increase in the γ-phase is observed with the powder recycling, which leads to a slight increase in ductility and decrease in hardness of the samples. Therefore, it is concluded that the 17-4 PH powder recycling process in SLM manufacturing is adequate and recommended to ensure the economic and environmental viability of the process without adversely affecting the properties of the parts.

Selective laser melting (SLM) is one of the additive manufacturing (AM) methods which is applicable to metal. This technique makes it possible to form complex internal shapes such as lattice structures. The lattice structure is expected to have weight reduction and vibration suppression effects on the product. In addition, a support structure is essential for the SLM fabrication process, which has the role of supporting the product and dissipating heat from the product. However, steep temperature gradients due to local laser irradiation and non-uniform heat conduction during the process can cause bending and cracking of the product. In particular, the support structure and lattice structure consisting of thin metal struts are greatly affected by process conditions, so it is necessary to select conditions suitable for stable and high-precision modeling. In this study, the influence of laser power and scanning speed on the mechanical characteristics of the support structure and lattice structure formed by SLM is investigated. In the tensile test of the support structure, a positive correlation with the volumetric energy density was confirmed, and suitable laser conditions were examined. In the compression test of the lattice structure, it was clear that the amount of energy absorption changed depending on the laser power, and the condition of 240 W achieved the maximum energy absorption.

A new class of martensitic stainless steel, namely 06Cr15Ni4CuMo, with applications in marine engineering, was processed by using selective laser melting (SLM). A body-centered cubic martensitic microstructure was observed, and the microstructure was compared with wrought 410 martensitic stainless steel. The SLM-processed sample showed a hardness of 465 ± 10 HV0.5, which was nearly 115 HV0.5 less than the wrought counterpart. Similarly, the SLM-processed sample showed improved YS and UTS, compared with the wrought sample. However, reduced ductility was observed in the SLM-processed sample due to the presence of high dislocation density in these samples. In addition, 71% volume high-angle grain boundaries were observed, corroborating the high strength of the material. The corrosion behavior was investigated in seawater, and the corrosion resistance was found to be 0.025 mmpy for the SLM-processed 06Cr15Ni4CuMo steel and 0.030 mmpy for wrought 410 alloys, showing better corrosion resistance in the SLM-processed material. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) is a technological process in which elements are fruitfully built-up adding materials layer by layer. AM had a massive development in recent times, thanks to its intrinsic advantages, especially if compared with conventional processes (i.e. subtractive manufacturing methods), in terms of free-form design, high customization of products, a significant reduction in raw materials consumption, low request of postprocessing and heat treatments, use of pure materials and reduced time for final products to be marketed. In order to give an innovative contribution to the knowledge in the field of metal AM materials, this paper reports the main outcomes of an experimental campaign focused on the influence of several specific printing parameters on the mechanical features of the 17-4PH stainless steel, which is one of the most used metal for the Selective Laser Melting (SLM) technology. The influence of different printing directions and sample inclinations on the material mechanical behavior is assessed, with the aim of considering an innovative use in the field of structural engineering. Moreover, the effects due to scanning and recoating times are studied. In addition, the consequences of heat treatment (annealing) on both the residual stresses and the amount of residual austenite are appraised.

The paper focuses on researching the effect of fatigue loading on metallic structure, lifetime, and fracture surface topographies in AISI H13 steel specimens obtained by selective laser melting (SLM). The topography of the fracture surfaces was measured over their entire area, according to the entire total area method, with an optical three-dimensional surface measurement system. The fatigue results of the SLM 3D printed steel specimens were compared with those reported for conventionally manufactured 13H steel. The investigation also considers the roughness of the specimens' side surface. Moreover, the fractographic evaluation conducted using scanning electron microscopy confirms that the predominant fracture mechanism is transgranular fracture. Microtomography done after mechanical loading also showed the influence of the stress level on the porosity distribution. Both fractographic and Micro-CT investigations confirm that higher stresses result in coarser and much more uniform porosity observed in fractured samples. These comprehensive quantitative and qualitative fracture analyses are beneficial to predict the failure conditions of SLM steel parts, especially in the case of fatigue damage. From the quantitative analysis of the H13 SLM-manufactured fracture surface topography, it was possible to conclude that the larger the loadings acting on the specimen, the rougher the fracture surface because the ductile fracture mode dominates. It has also been proven that the porosity degree changes along the length of the sample for the most stressed specimens. [ABSTRACT FROM AUTHOR]

The optimal SLM conditions of 304L stainless steel were obtained by single factor and orthogonal tests. Results indicated that the optimal hardness (75 HRB) and Relative Density (RD 99.24%) could be obtained when the laser output power was 190 W, the scanning distance was 0.09 mm and the scanning speed was 800 mm/s. The microstructure of fish scales was uniform and compact with a few pores in the optimal sample. The fine particles were randomly distributed near the edge of the molten pool, and some preferred granular columnar crystal structures were formed. Abundant entanglement dislocations were observed between cell structures, forming dislocation clusters. Spherical nano-precipitates, rich in Si, Mn, and O, were also observed near cell structures. The mechanical properties of the specimens were highly anisotropic, and there were obvious necking and ductility at the tensile fracture.

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Selective laser melting (SLM) is a promising additive manufacturing process for fabricating complex geometries of metallic parts. The SLM processing parameters can have a major effect on microstructure and mechanical behavior of the fabricated metallic parts. In this work, the effect of laser spot size, hatch spacing, energy density, scan strategy, scanning speed and laser power on the microstructure and mechanical behavior of SLM-processed 316L stainless steel samples has been studied. These samples processed with different processing parameters were characterized by performing microhardness, tensile tests, x-ray diffraction (XRD) analysis, Energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) analysis. The samples fabricated with a larger laser spot size exhibited higher tensile strength as well as higher microhardness values. A similar trend was observed for samples processed with higher laser power and hatch spacing. For the same energy density, higher laser power and lower scanning speed significantly enhance the mechanical properties of SLM processed samples compared to those fabricated with lower laser power and higher scanning speed. Therefore, it can be concluded that laser power has a more dominant role in governing the mechanical properties of SLM processed parts than scanning speed. [ABSTRACT FROM AUTHOR]

Owing to their lightweight design, high energy absorption capacity, and excellent thermal and sound insulation properties, lattice structures have many potential applications in the fields of security, aerospace, biomedicine, and heat dissipation. In this study, a gyroid-type triply periodic minimal surface is used to design lattice structures. Gyroid uniform lattice structures and gyroid graded lattice structures are mathematically designed and fabricated using selective laser melting with a SS 316 L stainless steel powder. The mechanical properties of these structures are studied under a compression load, and the deformation differences between the graded and uniform structures are compared. The finite element method is used to simulate the compression process, and the experimental and simulation results are qualitatively compared. Results show that during plastic deformation, the stress change in the graded structure is larger than that in the uniform structure. By controlling the volume fraction, mechanical properties can be specifically tailored, which provides the design guidelines for the application of this structure.

This work aims to compare the mechanical behavior of an AISI H13 steel obtained by additive manufacturing with that obtained by conventional manufacturing methods. The average values of the ultimate tensile strength (UTS) and ductility obtained for the specimens produced by the conventional method were equal to 658 MPa and 18%, respectively, which compares with 503 MPa and 0.75% registered for the selective laser melting (SLM) specimens. Inversely, the average hardness value determined for the SLM specimens was higher, 450 HV, than the observed for the conventional, 200 HV. In addition, the maximum applied stress corresponding to a fatigue limit's endurance of 2 × 106 cycles was equal to 340 and 85 MPa for conventional and SLM specimens, respectively. Therefore, from a fatigue design point of view, it was possible to infer that σmax/UTS = 0.17 for the SLM specimens tested. Porosity and lack of fusion influenced the static and the fatigue strength negatively in the SLM specimens. Highlights: An AISI H13 steel was obtained through conventional methods and by selective laser melting.A comparison between their static and the fatigue behavior was carried out.Fatigue design curves were obtained for specimens produced by SLM and conventional methods.A fatigue design recommendation for additively manufactured AISI H13 was made. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) is a technological process in which elements are fruitfully built-up adding materials layer by layer. AM had a massive development in recent times, thanks to its intrinsic advantages, especially if compared with conventional processes (i.e. subtractive manufacturing methods), in terms of free-form design, high customization of products, a significant reduction in raw materials consumption, low request of postprocessing and heat treatments, use of pure materials and reduced time for final products to be marketed. In order to give an innovative contribution to the knowledge in the field of metal AM materials, this paper reports the main outcomes of an experimental campaign focused on the influence of several specific printing parameters on the mechanical features of the 17-4PH stainless steel, which is one of the most used metal for the Selective Laser Melting (SLM) technology. The influence of different printing directions and sample inclinations on the material mechanical behavior is assessed, with the aim of considering an innovative use in the field of structural engineering. Moreover, the effects due to scanning and recoating times are studied. In addition, the consequences of heat treatment (annealing) on both the residual stresses and the amount of residual austenite are appraised. [ABSTRACT FROM AUTHOR]

The high solidification rate of selective laser melting (SLM) induces a nonequilibrium microstructure in as‐fabricated Ti alloys. Herein, a metastable β Ti–5Al–5Mo–5V–3Cr–1Zr alloy is successfully fabricated by SLM on a preheated substrate at 700 °C. The effects of preheating temperature on microstructure and mechanical properties of as‐fabricated specimens is systematically studied. The phase identification and electron microscopic results demonstrate that the 700 °C preheating temperature enables the transformation of metastable β structure into an α + β structure with massive amounts of nanosized α precipitates. Consequently, the SLM‐fabricated specimen after preheating process possesses higher ultimate tensile strength and hardness at 1440 MPa and 8.24 GPa, respectively. This work shows an alternative for SLM to tackle nonequilibrium microstructure and to increase the strength of metastable Ti alloys by introducing high temperature preheating. [ABSTRACT FROM AUTHOR]

A new class of martensitic stainless steel, namely 06Cr15Ni4CuMo, with applications in marine engineering, was processed by using selective laser melting (SLM). A body-centered cubic martensitic microstructure was observed, and the microstructure was compared with wrought 410 martensitic stainless steel. The SLM-processed sample showed a hardness of 465 ± 10 HV0.5, which was nearly 115 HV0.5 less than the wrought counterpart. Similarly, the SLM-processed sample showed improved YS and UTS, compared with the wrought sample. However, reduced ductility was observed in the SLM-processed sample due to the presence of high dislocation density in these samples. In addition, 71% volume high-angle grain boundaries were observed, corroborating the high strength of the material. The corrosion behavior was investigated in seawater, and the corrosion resistance was found to be 0.025 mmpy for the SLM-processed 06Cr15Ni4CuMo steel and 0.030 mmpy for wrought 410 alloys, showing better corrosion resistance in the SLM-processed material.

The lattice structures obtained by combining repetitive light cellular forms provide superior high strength to weight capabilities compared to monolithic solid bodies. These properties of lattice structures can be further enhanced by improving the design and manufacturing process. However, the process of creating aluminum alloy lattice structures with tailored mechanical properties is still challenging due to the wide range of possible designs and their complex structure-property relationships. This paper proposes a new methodology that uses the deep learning-based 3D Generative Adversarial Network (3DGAN) model to solve this complex engineering problem. Unlike previous studies on deep learning-based lattice design, the dataset obtained through parametric design and Simulated Annealing techniques enables GAN to create new 3D lattice structures with improved mechanical strength properties. The designs generated with the GAN algorithm were produced using Selective Laser Melting Additive Manufacturing (SLM-AM) technology. The mechanical properties of SLM-fabricated (SLMed) AlSi10Mg unit cell samples were examined by a series of compression and impact tests. The results reveal that the lattice configurations generated using the generative model exhibit improved mechanical properties (e.g., a remarkable increase in normalized energy absorption and extension capacities of up to 57% and 26%, respectively). This study shows that designs generated with the 3DGAN model in lattice structures improve the design space by improving their mechanical properties. Moreover, the successful integration of deep learning and SLM-AM opens up new possibilities for creating custom parts with improved strength-to-weight ratios, dimensional accuracy, and mechanical performance. [ABSTRACT FROM AUTHOR]

Selective laser melting is one of the additive manufacturing technologies that is used to produce complex -shaped components for applications in the automotive industry. The purpose of the changes in the design, technology, and material tests was to make a steering gear housing using the SLM method. The steering gear housing was produced by the pressure casting method using an AlSi9Cu3(Fe) alloy. The construction of this housing is adapted to the specifics of left-hand traffic. The change in technology was related to the change of the position of the steering system from right -hand to left-hand and the demand for a limited number of gear housings. It was necessary to make a virtual model of the housing on the basis of the part that was removed from the vehicle. In SLM technology, the AlSi10Mg aluminum alloy was used as a raw material in the form of CL 32Al gas -atomized powder. After the SLM process was completed, the housings were subjected to heat treatment. The AlSi10Mg alloy fabricated by the SLM method after heat treatment is characterized by good plasticity and an average value of tensile strength. The last stage was to check the geome try of the SLM housing with a 3D scanner. As a result, a map of the dimensional deviations from the nominal values was obtained. This data was used to modify the CAD model before the next fabrication process. The use of 3D printing technology allowed for the quick production of elements. The time to develop the technology and the production of the first two gear housings based on a 3D model was seven days. [ABSTRACT FROM AUTHOR]

In this work, hot isostatic pressing (HIP) treatment was performed on the TiC/GTD222 nickel-based composite prepared by selective laser melting (SLM). The effect of HIP on the microstructures and mechanical properties of the SLMed composite was investigated using XRD, SEM, EBSD and TEM. The results show that the microstructures of both SLMed and HIP-SLMed composites are composed of γ matrix, γ′ phase and carbides. The HIP treatment can significantly promote the formation of nanoscale carbides and γ′ phase, and simultaneously decrease the dislocation density of the composite. The yield strength and tensile strength of the HIP-SLMed composite increase by approximately 75 MPa and 189 MPa, respectively, while the elongation remains similar to that of the SLMed composite. The enhanced mechanical properties of the HIP-SLMed composite can be primarily attributed to the precipitation strengthening of the γ′ phase and the Orowan strengthening effect of the carbides. The microscopic deformation and strengthening mechanisms of the composites were also studied in detail. • HIP treatment has no obviously change in the average grain size of γ matrix. • HIP treatment promotes the formation of carbide and γ′ precipitation and reducing substructure and dislocation densities. • The HIP-SLMed composite has similar elongation (6.5 %) and slightly higher yield strength compared to SLMed composite. • The tensile strength of HIP-SLMed composite is 189 MPa higher than SLMed samples. • The precipitation strengthening and Orowan strengthening contribute significantly to the enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

This study investigated the microstructure, mechanical properties, impact toughness, and erosion characteristics of Al-10Si-Mg alloy specimens manufactured using the selective laser melting (SLM) method with or without subsequent T6 heat treatment. Furthermore, the erosion phase transformation behavior of the test specimens was analyzed, and the effect of the degradation mechanism on the tensile mechanical properties and impact toughness of the SLM Al-10Si-Mg alloy specimens before and after particle erosion was compared. The experimental results indicated that the Al-10Si-Mg alloy subjected to T6 heat treatment has better erosion resistance than the as-fabricated material. The tensile strength and fracture toughness of both specimen groups decreased due to the formation of microcracks on the surface caused by particle erosion. Nevertheless, the erosion-induced silicon nanoparticle solid solution softens the Al matrix and improves the elongation of the SLM Al-10Si-Mg alloy.

This study reports fabrication, mechanical characterization, and finite element modeling of a novel lattice structure based bimetallic composite comprising 316L stainless steel and a functional dissolvable aluminum alloy. A net-shaped 316L stainless steel lattice structure composed of diamond unit cells was fabricated by selective laser melting (SLM). The cavities in the lattice structure were then filled through vacuum-assisted melt infiltration to form the bimetallic composite. The bulk aluminum sample was also cast using the same casting parameters for comparison. The compressive and tensile behavior of 316L stainless steel lattice, bulk dissolvable aluminum, and 316L stainless steel/dissolvable aluminum bimetallic composite is studied. Comparison between experimental, finite element analysis (FEA), and digital image correlation (DIC) results are also investigated in this study. There is no notable difference in the tensile behavior of the lattice and bimetallic composite because of the weak bonding in the interface between the two constituents of the bimetallic composite, limiting load transfer from the 316L stainless steel lattice to the dissolvable aluminum matrix. However, the aluminum matrix is vital in the compressive behavior of the bimetallic composite. The dissolvable aluminum showed higher Young’s modulus, yield stress, and ultimate stress than the lattice and composite in both tension and compression tests, but much less elongation. Moreover, FEA and DIC have been demonstrated to be effective and efficient methods to simulate, analyze, and verify the experimental results through juxtaposing curves on the plots and comparing strains of critical points by checking contour plots.

Copyright of Journal of Zhejiang University: Science B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Additive/subtractive hybrid manufacturing technology is a new technology that combines product design, software control, and additive manufacturing (AM) with subtractive technology, which can realize the metallurgical bonding of dissimilar materials. In this study, hybrid parts made of two materials were fabricated by depositing CuCrZr on a 316 L stainless steel substrate by selective laser melting (SLM) technology. The microstructure and mechanical properties of the SLM-ed CuCrZr, 316 L matrix components and the 316 L/CuCrZr interface were studied. The microstructure of SLM-ed CuCrZr consisted of elongated columnar crystals that developed along the building direction, and the 316 L matrix material was characterised by large equiaxed grains. After the 316 L substrate was polished, there were no macroscopic cracks and only a few pores at the interface of 316 L/CuCrZr, and good metallurgical bonding was achieved. The complex and uneven metal flow occurred inside the molten pool because of the Marangoni effect under the action of the laser, resulting in drastic changes in the grain size at the interface. • CuCrZr alloy was fabricated by SLM on the 316 L substrate to achieve hybrid manufacturing. • Substrate surface state can influence interface of 316 L/CuCrZr. • Dendritic microcracks and pores are the main defects at the interface. • Difference in physical properties of materials and stress caused cracks. [ABSTRACT FROM AUTHOR]

Abstract The proposed paper deals with the experimental determination of process parameters reaching densities >99 % for Scandium modified aluminum alloy (Scalmalloy®) processed by SLM 280HL. The alloy achieves significantly higher yield strength and higher elongation than the AlSi10Mg aluminum alloy figcommonly used. Potential of this alloy is for lightweight applications in space, aerospace, and automotive industries, where is a need of the best possible stiffness to weight ratio. Experiments were provided with different values of laser power and laser scanning speed. Layer thickness and other parameters stayed unchanged. The X-ray micro-computed tomography (μCT) scanning of the tensile specimen was used in order to obtain qualitative and quantitative information about the porosity. [ABSTRACT FROM AUTHOR]

In order to improve the mechanical compatibility of the metallic implants with the human bone and avoid stress shielding effect，porous Ti6Al4V specimens was fabricated by using selective laser melting (SLM). Scanning electron microscope (SEM) was used to examine porous structures. The mechanical properties were also analyzed. It was found that the porosity of the SLMed specimens was about 46 % 9 which was decreased by 1 6 % as compared with the original designation. The decrease of porosity could be attributed to the scanning strategy，shape and size of the melting pool and the particles sticking to the surface. Microhardness of the longitudinal section (parallel to the build direction) was higher than that of the cross section (perpendicular to the build direction). As shown by compression tests，the elastic modulus and yield strength of the as-SLMed porous Ti6Al4V alloy were 8.8 GPa and 348 MPa, respectively, which were much closer to the properties of the nature bones than those of dense TC4 were. However，these measured properties deviated from the calculated values. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The microstructure and mechanical properties of Al-20Si produced by selective laser melting (SLM) are investigated for different heat treatment conditions. As a result of the high cooling rate during processing, the as-built SLM material displays a microstructure consisting of a supersaturated Al(Si) solid solution along with heavily refined eutectic Si and Si particles. The Si particles become coarser, and the eutectic Si gradually changes its morphology from fibrous to plate-like shape with increasing annealing temperature. The microstructural variations occurring during heat treatment significantly affect the mechanical behavior of the samples. The yield and ultimate strengths decrease from 374 and 506 MPa for the as-built SLM material to 162 and 252 MPa for the sample annealed at 673 K, whereas the ductility increases from 1.6 to 8.7%. This offers the possibility to tune microstructure and corresponding properties of the Al-20Si SLM parts to meet specific requirements.

In this study, a combination of Al−12Si and Al−20Si (Al−(12-20)Si) alloys was fabricated by selective laser melting (SLM) as a result of increased component requirements such as geometrical complexity and high dimensional accuracy. The microstructure and mechanical properties of the SLM Al−(12-20)Si in as-produced as well as in heat-treated conditions were investigated. The Al−(12-20)Si interface was in the as-built condition and it gradually became blurry until it disappeared after heat treatment at 673 K for 6 h. This Al−(12-20)Si bi-material displayed excellent mechanical properties. The hardness of the Al−20Si alloy side was significantly higher than that of the Al−12Si alloy side and the disparity between both sides gradually decreased and tended to be consistent after heat treatment at 673 K for 6 h. The tensile strength and elongation of the Al−(12-20Si) bi-material lies in between the Al−12Si and Al−20Si alloys and fracture occurs in the Al−20Si side. The present results provide new insights into the fabrication of bi-materials using SLM.

The influences of processing parameters such as volumetric energy density (ε) and, particularly, defocusing amount (DA) on densification, microstructure, tensile property, and hardness of the as-printed dense AlSi10Mg alloy by selective laser melting (SLM) were studied systematically. The molten pool boundaries (MPBs) were found overwhelmingly at regular and complex spatial topological structures affected by DA value to exist in two forms, while the “layer–layer” MPB overlay mutually and the “track–track” MPBs intersect to form acute angles with each other. The microstructure of MPBs exhibits a coarse grain zone near the MPBs and the characteristics of segregation of nonmetallic elements (O, Si) where the crack easily happened. The DA value (−2 to 2 mm) affected both the density and the tensile mechanical properties. High tensile strength (456 ± 14 MPa) and good tensile ductility (9.5 ± 1.4%) were achieved in the as-printed condition corresponding to DA = 0.5 mm. The tensile fracture surface features were analyzed and correlated to the influence of the DA values.