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Diffusion bonding of additive manufactured (AM) metal parts to traditionally manufactured metal parts is an effective and low-cost way to produce large-scale and multi-functional parts. In this study, diffusion bonding of casting 45 steel and AMed 316L stainless steel was conducted with four different bonding surface roughness from large to small. The interface formation mechanisms including the metallic elements diffusion layer, the carbide layer and the interfacial grain boundary (IGB) migration were investigated in detail. The results show that the interface bonding ratio improves from 43 to 96% due to void closure as the roughness of the bonding surface decreases from Ra ~ 1.5 µm to Ra ~ 0.1 µm. The shear strength of the joint increases from 350 to 468 MPa, and the specific shear strength increases from 58 to 94%. The type and number of grain boundary migrations are significantly affected by the bonding surface roughness. The number of IGB migrations at the "triple junction" structure increases while the number of strain-induced grain boundary migrations decreases as the bonding surface becomes smoother. [ABSTRACT FROM AUTHOR]

Lignocellulosic waste materials are among the most abundant raw materials on Earth, and they have been widely studied as natural additives in materials, especially for polymer composites, with interesting results when it comes to improving physiochemical properties. The main components of these materials are cellulose, hemicellulose, and lignin, as well as small amounts of other polysaccharides, proteins, and other extractives. Several kinds of lignocellulosic materials, mainly fibers, have been evaluated in polymer matrices, and recently, the use of particles has increased due to their high surface area. Garlic is a spice seed that generates a waste husk that does not have applications, and there are no reports of industrial use of this kind of lignocellulosic material. Additive manufacturing, also known as 3D printing, is a polymer processing technique that allows for obtaining complex shapes that are hard to obtain with ordinary techniques. The use of composites based on synthetic polymers and lignocellulosic materials is a growing field of research. In the present work, the elaboration and evaluation of 3D-printed polypropylene–garlic husk particle (PP-GHP) composites are reported. First, the process of obtaining a filament by means of a single extrusion was carried out, using different GHP contents in the composites. Once the filament was obtained, it was taken to a 3D printer to obtain probes that were characterized using differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) was performed with the aim of evaluating the thermal behavior of the 3D-printed PP-GHP composites. According to the obtained results, the crystallization process and thermal stability of the PP-GHP composites were modified with the presence of GHP compared with pristine PP. Dynamic mechanical analysis (DMA) showed that the addition of GHP decreased the storage modulus of the printed composites and that the Tan δ peak width increased, which was associated with an increase in toughness and a more complex structure of the 3D-printed composites. X-ray diffraction (XRD) showed that the addition of GHP favored the presence of the β-phase of PP in the printed composites. [ABSTRACT FROM AUTHOR]

Laser metal deposition (LMD) provides an emerging opportunity for the economic fabrication of high-value components at low production volume. Despite the technical and commercial opportunities associated with LMD, there exist potential failure-modes that differ from those typical of traditional manufacture; concurrently, LMD is typically applied to high-value components associated with a high consequence of failure. This report contributes to the emerging literature on LMD component design and failure analysis by documenting the design and destructive testing of a high-value tensile loaded hook component, including numerical structural simulation, manufacture characterisation, microstructural analysis and instrumented destructive testing. This systematic design contributes to the understanding of LMD design for structural integrity and supports the application of LMD as a robust commercial additive technology. [ABSTRACT FROM AUTHOR]

The directed energy deposition arc (DED-Arc) has been extensively used to develop metallic parts with varying complexities. A major challenge for austenitic stainless steels is managing heat accumulation due to their low thermal conductivity. This study aimed to characterize the microstructure and mechanical properties of AISI 316L preforms manufactured by additive manufacturing (AM) under different deposition paths and cooling conditions. Samples underwent macro- and microstructural analyses, and tensile and hardness tests to evaluate their mechanical behavior. Additionally, the effect of active cooling using near immersion active cooling (NIAC) in water on the microstructure was assessed by examining the secondary interdendritic spacing and ferritic phase fraction. The NIAC technique has shown potential for enhancing productivity by producing preforms with more uniform thickness and consistent solidification/cooling conditions throughout the multiple layers. This approach eliminated deposition idle time, leading to a productivity increase of up to 108%. Microstructures obtained with active cooling were more refined than those resulting from natural cooling, evidenced by a reduction in secondary interdendritic spacing and an increased fraction of delta ferrite. These microstructural changes resulted in higher hardness and mechanical strength in the material processed with the NIAC technique. However, difficulties in precisely controlling the water level resulted in increased apparent porosity when using the NIAC technique. [ABSTRACT FROM AUTHOR]

Hemodialysis (HD) is a treatment supporting decreased kidney function, via a catheter inserted into the heart’s Right Atrium (RA). Recirculation is a source of inefficiency for treatment, where blood is dialyzed again due to poor catheter design. Lab-testing is still relatively unexplored, hence, a mechanical testing system was designed with the intention of providing a consistent and repeatable environment for testing HD catheters. System geometry was composed using a Computer-Aided Design (CAD) model of a heart, with the RA scaled to appropriate dimensions, and a PolyDiMethylSiloxane (PDMS) model produced through 3D printing and negative wax casting. Pulsatile blood flow was mimicked by peristaltic pumps driving a blood analogue (BA). Recirculation was induced by adding dyed BA to the system via the catheter and measured using a colorimeter. The developed platform was initially evaluated using two catheters, demonstrating the capability to accurately replicate atrial hemodynamic conditions. Two step-tipped catheters, A and B, were tested at 350 ml/min, producing recirculation values of 13.11% and 18.58%, respectively. The results exhibit the ability of the system developed to evaluate HD catheter performance, with the potential to explore a wider range of tip geometries relevant to clinical preference. Furthermore, this advancement towards an anatomically accurate lab-based test system could be paired with computational methods to progress the evaluation of such medical devices and enhance their development. [ABSTRACT FROM AUTHOR]

Magnesium alloys, renowned for their lightweight yet high-strength characteristics, with exceptional mechanical properties, are highly coveted for numerous applications. The emergence of magnesium alloy additive manufacturing (Mg AM) has further propelled their popularity, offering advantages such as unparalleled precision, swift production rates, enhanced design freedom, and optimized material utilization. This technology holds immense potential in fabricating intricate geometries, complex internal structures, and performance-tailored microstructures, enabling groundbreaking applications. In this paper, we delve into the core processes and pivotal influencing factors of the current techniques employed in Mg AM, including selective laser melting (SLM), electron beam melting (EBM), wire arc additive manufacturing (WAAM), binder jetting (BJ), friction stir additive manufacturing (FSAM), and indirect additive manufacturing (I-AM). Laser powder bed fusion (LPBF) excels in precision but is limited by a low deposition rate and chamber size; WAAM offers cost-effectiveness, high efficiency, and scalability for large components; BJ enables precise material deposition for customized parts with environmental benefits; FSAM achieves fine grain sizes, low defect rates, and potential for precision products; and I-AM boasts a high build rate and industrial adaptability but is less studied recently. This paper attempts to explore the possibilities and challenges for future research in AM. Among them, two issues are how to mix different AM applications and how to use the integration of Internet technologies, machine learning, and process modeling with AM, which are innovative breakthroughs in AM. [ABSTRACT FROM AUTHOR]

An efficient and successful electrochemical process must take place in an electrochemical reactor with an adapted and optimized design that allows superior performance to be achieved. Traditional manufacturing methods have made the task of optimizing and adapting reactors very expensive. However, 3D printing allows prototypes to be built in a very short time and at a very low cost compared to traditional manufacturing techniques. This has caused research into new electrochemical reactors in different laboratories to skyrocket in recent years. The rapid evolution of 3D printing technology, as well as the appearance of new materials, have meant that they can be included in many applications, such as the electrochemical treatment of contaminated water or energy devices, batteries or fuel cells. In this review, the latest advances in the manufacture of electrochemical reactors and the main applications that have made use of them will be presented and critically discussed. [ABSTRACT FROM AUTHOR]

Purpose – As an advanced manufacturing method, additive manufacturing (AM) technology provides new possibilities for efficient production and design of parts. However, with the continuous expansion of the application of AM materials, subtractive processing has become one of the necessary steps to improve the accuracy and performance of parts. In this paper, the processing process of AM materials is discussed in depth, and the surface integrity problem caused by it is discussed. Design/methodology/approach – Firstly, we listed and analyzed the characterization parameters of metal surface integrity and its influence on the performance of parts and then introduced the application of integrated processing of metal adding and subtracting materials and the influence of different processing forms on the surface integrity of parts. The surface of the trial-cut material is detected and analyzed, and the surface of the integrated processing of adding and subtracting materials is compared with that of the pure processing of reducing materials, so that the corresponding conclusions are obtained. Findings – In this process, we also found some surface integrity problems, such as knife marks, residual stress and thermal effects. These problems may have a potential negative impact on the performance of the final parts. In processing, we can try to use other integrated processing technologies of adding and subtracting materials, try to combine various integrated processing technologies of adding and subtracting materials, or consider exploring more efficient AM technology to improve processing efficiency. We can also consider adopting production process optimization measures to reduce the processing cost of adding and subtracting materials. Originality/value – With the gradual improvement of the requirements for the surface quality of parts in the production process and the in-depth implementation of sustainable manufacturing, the demand for integrated processing of metal addition and subtraction materials is likely to continue to grow in the future. By deeply understanding and studying the problems of material reduction and surface integrity of AM materials, we can better meet the challenges in the manufacturing process and improve the quality and performance of parts. This research is very important for promoting the development of manufacturing technology and achieving success in practical application.

Additive Manufacturing (AM) is receiving widespread attention from both industry and academia who are looking to benefit from the numerous advantageous possibilities that AM processes have to offer, such as the potential to design and produce highly complex bespoke geometries with minimal material wastage. Yet, despite this, AM also has some drawbacks. Some of the most significant include the presence of process-induced defects and the inherent surface roughness of an AM built component, both of which can have a considerable influence on the mechanical properties of the final product. This research will investigate the role of an as-built surface on the fatigue properties of AM Ti–6Al–4V manufactured by electron beam melting (EBM), laser powder bed fusion (L-PBF) and laser metal deposition with wire (LMD-w). Fatigue results have been generated alongside advanced surface profilometry, microstructural, defect and fractographic analyses that have revealed that whilst the surface roughness in the majority of instances is the primary factor impacting the fatigue performance on AM material, it cannot be considered alone. It was found that the inherent as-built (AB) surface finish was significantly different across the various AM processes, inducing a range of effective stress concentrations and thus, a contrasting impact on the resulting fatigue performance. Results from each variant have been compared against a machined and polished equivalent, to provide a further consideration as to whether the as-built surface would be suffice from a time and economical viewpoint. Statistical analysis of the generated results also allowed for an extrapolation of predicted fatigue lives in the very high cycle regime for the alternative AM Ti–6Al–4V variants.

Carbon nanofibers (CNFs) and graphene nanosheets (GNs) are introduced to obtain nano-sized TiC particles in a novel additive manufactured Ni-Co-based superalloy. The double strengthening effects of reaction-induced TiC and remaining CNFs/GNs are conceptualized in the present paper. The CNFs and GNs act as heterogeneous nucleation sites for the formation of uniformly distributed TiC nanoparticles, which inhibits the crack and homogenize the microstructure. Interestingly, the existence of remaining GNs/CNFs is revealed via 3D atom-by-atom tomographic reconstruction technology for the first time. This unique combination of nanoparticles and residual CNFs/GNs nanofillers has great potential to develop superalloys with excellent properties.

Diffusion bonding of additive manufactured (AM) metal parts to traditionally manufactured metal parts could simultaneously achieve large-scale, complex-structure, and multi-material parts. However, there is a lack of study on diffusion bonding as well as its interface formation mechanism between AM metal parts and traditionally manufactured metal parts. In this study, diffusion bonding was performed to join AM 316L stainless steel and casting 45 steel at different temperatures. The element distribution, interface characteristics and shear strength of the joints were investigated, and the interface formation mechanism at different bonding temperature was analyzed in detail. The results reveal that the interface transition zone from the AM 316L steel side to the 45 steel side is composed of the metallic elements diffusion layer and the carbide layer. Moreover, an increase in bonding temperature can effectively promote interface voids closure and increase the thickness of the metallic elements diffusion layer, while the thickness of the carbide layer firstly increases and then decreases as the temperature increases. The component of the carbide layer was identified as brittle compounds (CrFe)23C6 and (CrFe)7C3. The shear strength of the joints exhibited an increasing trend with the increasing bonding temperature. Interestingly, a sudden decrease in strength was found at 950 °C due to the significant increase of the brittle carbide layer, while high-quality joints could be achieved as the brittle carbides dissolve at 1000 °C. This study could lay the foundation for understanding diffusion bonding interface behaviors between AM metal parts and traditional casting metal parts.

Electrochemical (EC) detection is a powerful tool supporting simple, low-cost, and rapid analysis. Although screen printing is commonly used to mass fabricate disposable EC chips, its mask is relatively expensive. In this research, we demonstrated a method for fabricating three-electrode EC chips using 3D printing of relatively high-viscosity paste. The electrodes consisted of two layers, with carbon paste printed over silver/silver chloride paste, and the printed EC chips were baked at 70 °C for 1 h. Engineering challenges such as bulging of the tubing, clogging of the nozzle, dripping, and local accumulation of paste were solved by material selection for the tube and nozzle, and process optimization in 3D printing. The EC chips demonstrated good reversibility in redox reactions through cyclic voltammetry tests, and reliably detected heavy metal ions Pb(II) and Cd(II) in solutions using differential pulse anodic stripping voltammetry measurements. The results indicate that by optimizing the 3D printing of paste, EC chips can be obtained by maskless and flexible 3D printing techniques in lieu of screen printing. [ABSTRACT FROM AUTHOR]

The introduction of additive technologies may require an update in the methods of developing heat exchangers (HE). A variant of the methodology of HE parametric design has been demonstrated on a Schwarz P-surface. A 3D-calculaiton of a row-by-row representative HE model has been used to obtain data for deriving empirical criterial dependences suited for a fast engineering calculation of HE thermohydraulic characteristics. Within the framework of the technological testing and approval of HE manufacture on Schwarz P-surfaces, possibilities have been demonstrated for their scaling and for a reduction in roughness in the course of postprocessing for different materials. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) and graphene nanosheets (GNs) are introduced to obtain nano-sized TiC particles in a novel additive manufactured Ni-Co-based superalloy. The double strengthening effects of reaction-induced TiC and remaining CNFs/GNs are conceptualized in the present paper. The CNFs and GNs act as heterogeneous nucleation sites for the formation of uniformly distributed TiC nanoparticles, which inhibits the crack and homogenize the microstructure. Interestingly, the existence of remaining GNs/CNFs is revealed via 3D atom-by-atom tomographic reconstruction technology for the first time. This unique combination of nanoparticles and residual CNFs/GNs nanofillers has great potential to develop superalloys with excellent properties. The formation of nano-sized dispersion TiC particles is induced by the introduction of carbon nanofibers and graphene nanosheets in additive manufactured superalloy, which inhibits the crack and homogenizes the microstructure. [ABSTRACT FROM AUTHOR]

Abstract An efficient and successful electrochemical process must take place in an electrochemical reactor with an adapted and optimized design that allows superior performance to be achieved. Traditional manufacturing methods have made the task of optimizing and adapting reactors very expensive. However, 3D printing allows prototypes to be built in a very short time and at a very low cost compared to traditional manufacturing techniques. This has caused research into new electrochemical reactors in different laboratories to skyrocket in recent years. The rapid evolution of 3D printing technology, as well as the appearance of new materials, have meant that they can be included in many applications, such as the electrochemical treatment of contaminated water or energy devices, batteries or fuel cells. In this review, the latest advances in the manufacture of electrochemical reactors and the main applications that have made use of them will be presented and critically discussed.

Direct comparisons are made between the crystallographic texture and residual stress distribution within two otherwise identical Inconel cubes produced by Selective Laser Melting (SLM) and Electron Beam Melting (EBM) additive manufacturing processes. In both respects, significant differences were observed; the SLM process produced a sample with high residual stress and cubic texture, while the EBM process generated negligible residual stress and a fibre texture. In the case of the SLM sample, the paper continues on to examine two different approaches to modelling the residual stress field; 1. a simplistic version based on an assumed radially symmetric isotropic eigenstrain, and 2. a layer-by-layer combined thermo-mechanical approach based on finite element modelling. Both models were able to capture the important overall features of the residual stress distribution, however the layer-by-layer approach showed more fidelity in the finer details.

AlSi10Mg porous protective structure often produces different damage forms under compressive loading, and these damage modes affect its protective function. In order to well meet the service requirements, there is an urgent need to comprehensively understand the mechanical behavior and response mechanism of AlSi10Mg porous structures under compressive loading. In this paper, AlSi10Mg porous structures with three kinds of volume fractions are designed and optimized to meet the requirements of high-impact, strong-energy absorption, and lightweight characteristics. The mechanical behaviors of AlSi10Mg porous structures, including the stress–strain relationship, structural bearing state, deformation and damage modes, and energy absorption characteristics, were obtained through experimental studies at different loading rates. The damage pattern of the damage section indicates that AlSi10Mg porous structures have both ductile and brittle mechanical properties. Numerical simulation studies show that the AlSi10Mg porous structure undergoes shear damage due to relative misalignment along the diagonal cross-section, and the damage location is almost at 45° to the load direction, which is the most direct cause of its structural damage, revealing the damage mechanism of AlSi10Mg porous structures under the compressive load. The normalized energy absorption model constructed in the paper well interprets the energy absorption state of AlSi10Mg porous structures and gives the sensitive location of the structures, and the results of this paper provide important references for peers in structural design and optimization. [ABSTRACT FROM AUTHOR]

Powder-bed binder-jetting 3D printing requires the use of a liquid binder or ink. These binders/inks have been widely tailored for individual application. This article covers the proof-of-concept development of an ink for a powder-bed binder-jetting 3D printer. The ink formulation in our work is both catalytically active and is used to bind the catalyst substrate. A modified, commercially available inkjet cartridge is used to spread liquid ink onto a powder surface, forming shapes in a layer-wise fashion to produce green bodies that are heat-treated post-print. The important parameters for manipulating rheology for inkjet printing are explored as a function of ink formulation. Specifically, the relationship between density, viscosity, and surface tension dictates the suitability for printing and those properties can be controlled by using differing amounts of the ink's constituent components. Relationships correlating density to solvent concentration and viscosity to binder and dispersant concentrations are found, which are used to determine a water-based ink formulation suitable for use in the commercially available ink cartridge. The results of an initial print are presented and show excellent dispersion of the nickel catalyst. [Display omitted] • Introducing an active metal precursor to the ink formulation for powder-bed binder-jetting can the catalyst infiltration step. • Feasibility was demonstrated using a Ni salt active metal precursor, alpha Al2O3 substrate, and rice starch pore former. • Within formulations tested, surface tension is independent of composition, while binder and solvent affect printability. • Addition of active metal precursor to the ink did not have a significant effect on its physical properties. • Targeting a Fromm's parameter of 4–10 resulted in a successful proof-of-concept 3D print with even catalyst distribution.. [ABSTRACT FROM AUTHOR]

This study presents a new solution to address challenges encountered in additive manufacturing, specifically in the context of 3D printing, where failures can occur due to complications associated with the nozzle or filament. The proposed solution in this research involves using a time-domain feature extraction method that leverages sound and vibration patterns. By implementing sensors to capture these signals in a controlled and noise-free environment, and then utilizing a Multi-Layer Perceptron (MLP) model trained accurately to predict upcoming signals and vibrations, proactive anticipation of printing outcomes is facilitated, including potential failures. Simulation results obtained using MATLAB for the MLP showcase the effectiveness of this approach, demonstrating remarkably low error rates. Furthermore, through rigorous data validation, the proposed method's ability to accurately identify sound and vibration signals is confirmed. As a result, the likelihood of failures is significantly reduced, thereby preventing defects in the filament. The implications of this solution hold great promise in substantially enhancing the reliability and efficiency of additive manufacturing processes. [ABSTRACT FROM AUTHOR]

This paper presents the design of fully metallic 3D Vivaldi antenna that can be used for wireless power transmission applications. The 3D antenna consists of 1) a tapered profile, 2) a rectangular cavity, and 3) a horizontal slot cut that is used as a transition between the cavity and the tapered profile. The proposed antenna design is fabricated using two distinct approaches, the first of which is a 3D metal additive manufacturing (AM scheme) with a sequential material layer addition technique. The second version is based on the CNC milling (CNCM) technique implemented by selectively removing material in a controlled way. The measured gain of the AM and CNCA-based 3D Vivaldi antenna is 4.95 dBi, and 5.70 dBi, respectively. The measured bandwidth (BW) of the AM-based 3D antenna is 4.70 GHz (fractional BW (FBW) of $52.86\%$ ), whereas the CNCM-based 3D antenna is 4.95 GHz (FBW of $56.73\%$ ). Measurement outcomes indicate that the CNCM version of the 3D Vivaldi antenna is $\sim ~1.2x$ more effective than the AM version in terms of realized gain and can be used for metal-based antenna system power telemetry due to its high gain and wide operational bandwidth capability.

Tribocorrosion is a type of material degradation caused by simultaneous wear and corrosion of metal surfaces caused by laminar or turbulent flow. Additive manufacturing technology plays an important role in its application to precision components and complex assemblies. This study developed a 316LX material with Fe, Ni, Cr, and other powder alloys that was processed into an ultra-protective wire as a 3D printing filler. This simulation of tribocorrosion conditions was performed on a triboester machine. This simulation is expected to provide important insights and understanding into the behavior and properties of the 316LX 3D printing material, especially when exposed to abrasion and corrosion conditions in a sulfuric acid solution environment. Corrosion Rate Testing of 316LX Material Additives Using Potentiodynamic Methods in a Modified Rotating 5% Sulfuric Acid Fluid. In addition to corrosion rate, the Vickers hardness, metallography, and shrinkage of the 316LX green part material were also tested at 1000oC after sintering.

An Al–Zn–Mg–Cu–Si–Zr–Er alloy was fabricated by laser powder bed fusion technology. A unique cellular structure consisting of α-Al, Mg2Si, and Al2CuMg phases was observed in both as-printed (AP) and direct aging (DA) alloys. Direct aging treatment at 150 °C × 4 h can improve the yield strength and hardness of the alloy, and precipitation strengthening and fine grain strengthening are dominant mechanisms. The strength of the regression re-aging (RRA) heat treated alloy decreased, while the elongation was obviously improved, and the grain boundary was continuous without precipitates free zones. DA could not significantly hinder the fatigue crack growth rate of the as-printed alloy, but the improvement of plasticity, elimination of residual stress, and the effect of precipitates in RRA alloy extend the life of the fatigue crack growth stage, thereby improving the overall fatigue life of the alloy from 1.17 × 105 cycles to 3.93 × 106 cycles.

Lignocellulosic waste materials are among the most abundant raw materials on Earth, and they have been widely studied as natural additives in materials, especially for polymer composites, with interesting results when it comes to improving physiochemical properties. The main components of these materials are cellulose, hemicellulose, and lignin, as well as small amounts of other polysaccharides, proteins, and other extractives. Several kinds of lignocellulosic materials, mainly fibers, have been evaluated in polymer matrices, and recently, the use of particles has increased due to their high surface area. Garlic is a spice seed that generates a waste husk that does not have applications, and there are no reports of industrial use of this kind of lignocellulosic material. Additive manufacturing, also known as 3D printing, is a polymer processing technique that allows for obtaining complex shapes that are hard to obtain with ordinary techniques. The use of composites based on synthetic polymers and lignocellulosic materials is a growing field of research. In the present work, the elaboration and evaluation of 3D-printed polypropylene–garlic husk particle (PP-GHP) composites are reported. First, the process of obtaining a filament by means of a single extrusion was carried out, using different GHP contents in the composites. Once the filament was obtained, it was taken to a 3D printer to obtain probes that were characterized using differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) was performed with the aim of evaluating the thermal behavior of the 3D-printed PP-GHP composites. According to the obtained results, the crystallization process and thermal stability of the PP-GHP composites were modified with the presence of GHP compared with pristine PP. Dynamic mechanical analysis (DMA) showed that the addition of GHP decreased the storage modulus of the printed composites and that the Tan δ peak width increased, which was associated with an increase in toughness and a more complex structure of the 3D-printed composites. X-ray diffraction (XRD) showed that the addition of GHP favored the presence of the β-phase of PP in the printed composites.

Magnesium alloys, renowned for their lightweight yet high-strength characteristics, with exceptional mechanical properties, are highly coveted for numerous applications. The emergence of magnesium alloy additive manufacturing (Mg AM) has further propelled their popularity, offering advantages such as unparalleled precision, swift production rates, enhanced design freedom, and optimized material utilization. This technology holds immense potential in fabricating intricate geometries, complex internal structures, and performance-tailored microstructures, enabling groundbreaking applications. In this paper, we delve into the core processes and pivotal influencing factors of the current techniques employed in Mg AM, including selective laser melting (SLM), electron beam melting (EBM), wire arc additive manufacturing (WAAM), binder jetting (BJ), friction stir additive manufacturing (FSAM), and indirect additive manufacturing (I-AM). Laser powder bed fusion (LPBF) excels in precision but is limited by a low deposition rate and chamber size; WAAM offers cost-effectiveness, high efficiency, and scalability for large components; BJ enables precise material deposition for customized parts with environmental benefits; FSAM achieves fine grain sizes, low defect rates, and potential for precision products; and I-AM boasts a high build rate and industrial adaptability but is less studied recently. This paper attempts to explore the possibilities and challenges for future research in AM. Among them, two issues are how to mix different AM applications and how to use the integration of Internet technologies, machine learning, and process modeling with AM, which are innovative breakthroughs in AM.

Seven formulations of ammonium perchlorate composite propellant (APCP) are developed and their properties relevant for successful additive manufacture are characterized. Extrusion in a custom‐built 3D printing system and spindle viscometry are used to collect viscosity measurements of curing primary and non‐curing secondary versions of the formulations. The formulations that behave similarly to a Bingham plastic, with apparent viscosities between 4 and 8 thousand Pa*s at 30 minutes post‐mix, are determined to be most suitable for printing applications. Measurements of one material show a yield stress of 1 kPa. Ambient pressure burn rates of 2.0–2.9 mm/s were measured for the compositions tested. All measured burn rates were comparable to the lower end of typical burn rates for APCP. The results of the characterization demonstrate a propellant suitable for use in a 3D printing system. [ABSTRACT FROM AUTHOR]

Binder jetting additive manufacturing (BJAM) is a widely studied technique fabricating metal parts. In this study, bimodal 316L stainless steel powder mixture of coarse (D50 – 34.1μm) and fine (D50 – 6.28μm) powders were designed for BJAM. Infiltration was used to improve the density of BJAMed parts. Bimodal powder mixture showed clear advantage over unimodal powder system on density and mechanical property of BJAMed parts. Upon solid-phase sintering, BJAMed 316 stainless steel of bimodal powder mixture (9:1 mass ratio of coarse to fine powder) showed relative density 97.19% and tensile strength 343.62 MPa, as compared with relative density 84.55% and tensile strength 291.59 MPa for pure coarse powder. For the same bimodal powder mixture, bronze infiltration, compared with solid-phase sintering, resulted in noticeably higher relative density 99.92% and tensile strength 621.63 MPa. Compared with solid-phase sintering, infiltration significantly reduced the volumetric shrinkage. [ABSTRACT FROM AUTHOR]

Launching satellites into the Earth's orbit is a critical area of research, and very demanding satellite services increase exponentially as modern society takes shape. At the same time, the costs of developing and launching satellite missions with shorter development times increase the requirements of novel approaches in the several engineering areas required to build, test, launch, and operate satellites in the Earth's orbit, as well as in orbits around other celestial bodies. One area with the potential to save launching costs is that of the structural integrity of satellites, particularly in the launching phase where the largest vibrations due to the rocket motion and subsequent stresses could impact the survival ability of the satellite. To address this problem, two important areas of engineering join together to provide novel, complete, and competitive solutions: topology optimisation methods and additive manufacturing. On one side, topology optimisation methods are mathematical methods that allow iteratively optimising structures (usually by decreasing mass) while improving some structural properties depending on the application (load capacity, for instance), through the maximisation or minimisation of a uni- or multi-objective function and multiple types of algorithms. This area has been widely active in general for the last 30 years and has two main core types of algorithms: continuum methods that modify continuous parameters such as density, and discrete methods that work by adding and deleting material elements in a meshing context. On the other side, additive manufacturing techniques are more recent manufacturing processes aimed at revolutionising manufacturing and supply chains. The main exponents of additive manufacturing are Selective Laser Melting (SLM) (3D printing) as well as Electron Beam Melting (EBM). Recent trends show that topology-optimised structures built with novel materials through additive manufacturing processes may provide cheaper state-of-the-art structures that are fully optimised to better perform in the outer-space environment, particularly as part of the structure subsystem of novel satellite systems. This work aims to present an extended review of the main methods of structural topology optimisation as well as additive manufacture in the aerospace field, with a particular focus on satellite structures, which may set the arena for the development of future satellite structures in the next five to ten years. [ABSTRACT FROM AUTHOR]

Integrating different matrices into fiber-reinforced plastics (FRP) offers great potential for general tailored functionalities. By locally integrating flexible matrix zones in otherwise stiff FRPs, both very stiff and flexible areas with properties such as bending and damping behavior can be achieved. A novel method for manufacturing these so-called multi-matrix composites (MMC) is presented in this work. Either manually or in an automated fashion a first matrix system is locally applied to fiber preforms. After curing these zones, all fiber areas that are still dry can be infiltrated with a second matrix system. In this manner a composite structure with different and defined matrix zones of almost any size and shape can be created. Experimentally, the integration of flexible polyurethane and stiff epoxy resin into glass fiber preforms was investigated, considering material compatibility and process precision. For an established process-chain, good infiltration quality with distinct transition zone between the matrices was verified, resulting in bending specimens showing deformation only in the regions of polyurethane elastomer matrix. [ABSTRACT FROM AUTHOR]

This letter explores the advantages of additively manufactured substrates with spatially varying electromagnetic properties. These engineered substrates will be constructed using space filling curves (SFC) of various orders. New advanced manufacturing systems such as the nScrypt 3Dn-300, have enabled the rapid fabrication of these SFC substrates. This letter will apply the engineered SFC substrate to the design and fabrication of metasurface antennas. By utilising a SFC to vary the local substrate permittivity, along with the printed conductive patch dimensions, the range of achievable surface impedances can be greatly expanded. This enlarged design space will be leveraged to yield increased gain for a given metasurface antenna size. Methods to characterise the substrate permittivity and conductive ink are discussed along with a complete description of the metasurface antenna design, fabrication and validation process.

Metallic powder for Additive Manufacturing (AM) typically varies between different batches, while being supplied to achieve the same customer specification. In order to reduce this variation and minimise waste, batches are often mixed together in both their virgin and used form. However, the properties of bulk components must have limited variance in order to be reliably used in an industrial setting. This manuscript is focused on the analysis of Grade 5 Ti6Al4V powders (3 virgin, plus 2 blends) and the associated mechanical properties of Electron Beam Melted (EBM) AM specimens. Measurements were performed in accordance with the principles defined in the MMPDS Handbook, ESDU database, and ASTM F2924. The tensile, and fatigue properties of the EBM specimens were found to be superior when compared with Ti6Al4V properties within these standards. This demonstrated that these powders are suitable for a wide range of commercial applications, and that these blended powders (including used powders) are able to achieve these requirements. Additionally, the results provide a systematic route for powder verification and highlight the importance of adhering to standardised principles and specifications to ensure quality and reliability in metallic AM materials.

It has been confirmed that micro-alloying is the effective way to refine the grain size and elevate the properties of pure Ti alloy produced via additive manufacturing. The pure Ti, Ti–2Fe (wt.%) and Ti–4Fe (wt.%) alloys created via Laser Melting Deposition (LMD) are compared based on their grain size, orientation relationship, and mechanical properties. Ti–4Fe displays a significantly lower average grain size of 220 μm in comparison to pure Ti and Ti–2Fe alloys, with average size of 442.3 and 319.6 μm. The superior constitutional supercooling of the former is responsible for the decrease in grain size. The orientation of the α phase is found to be influenced by the solid solution of Fe, with greater Fe content resulting in a preference towards the (0 0 0 1) direction for growth. Furthermore, the inclusion of Fe led to a noteworthy increase in both the yields strength, peaking at 798 MPa, and tensile strength, reaching 880 MPa. This enhancement is attributed to both the fine grain strengthening (54.4%) and the solid solution strengthening of Fe atoms (45.6%).

2319 aluminum alloy was prepared using wire arc additive manufacturing (WAAM) technique. The solid solution time of achieving improving corrosion resistance in WAAM 2319 aluminum alloy was investigated. The results indicated that the as deposited 2319 aluminum alloy was composed of dendritic grains. Numerous inter-granular intermetallic were continuously distributed along the grain boundary. As the solid solution time increased, the inter-granular intermetallic gradually dissolved into α-Al matrix resulting in discontinuously distribution and more homogeneous element distribution. Electrochemical experiment results indicated that the corrosion potential of WAAM 2319 aluminum alloy gradually increased with the increase of solid solution time. This indicated that increasing solid solution time could effectively increased the corrosion resistance of WAAM 2319 aluminum alloy. Improved corrosion resistance can be attributed to refined and discontinuous inter-granular intermetallic.

Ceramics are highly regarded in dental restorations owing to their favorable mechanical properties, chemical resistance, biocompatibility, and aesthetic features. Ceramic additive manufacturing (AM) technology has emerged as a promising solution that offers advantages over traditional techniques such as injection molding, die pressing, tape casting, and milling. Ceramic AM is, however, still under development, with new technologies and devices continuously emerging. This paper provides a comprehensive review of the latest research and applications of ceramic AM in dental restoration, focusing on the progress made within the past five years. Three perspectives are discussed: ceramic AM technologies, commonly used printable ceramic materials, and different types of dental restorations. Among these, vat photopolymerization is the most widely researched and promising AM technology for large-scale applications. ZrO2 remains the primary material used in AM research, whereas crowns and bridges are the most frequently studied and are the closest to industrialized dental restorations. Currently, ceramic AM satisfies the clinical requirements of accuracy, mechanical performance, and biocompatibility. However, compared with traditional methods, it lacks significant advantages in terms of cost and manufacturing efficiency, limiting its large-scale application. Further improvements are necessary in all stages, including raw materials, equipment, post-processing, and standardization.

Additive manufacturing (3D printing) has been deployed across multiple platforms to fabricate bioengineered tissues. We demonstrate the use of a Thermal Inkjet Pipette System (TIPS) for targeted delivery of cells onto manufactured substrates to design bio-bandages. Two cell lines – HEK 293 (kidney) and K7M2 wt (bone) – were applied using TIPS. We demonstrate a novel means for targeted cell delivery to a hydrogel support structure. These cell/support constructs (bio-bandages) had a high viability for survival and growth over extended periods. Combining a flexible biosupport with application of cells via TIPS printing now for the first time allows for custom cell substrate constructs with various densities to be deployed for regenerative medicine applications.

The development of miniaturized, sustainable and eco-friendly analytical sensors with low production cost is a current trend worldwide. Within this idea, this work presents the innovative use of masked stereolithography (MSLA) 3D-printed substrates for the easy fabrication of pencil-drawn electrochemical sensors (MSLA-3D-PDE). The use of a non-toxic material such as pencil (electrodes) together with a biodegradable 3D printing resin (substrate) allowed the production of devices that are quite cheap (ca. US$ 0.11 per sensor) and with low environmental impact. Compared to paper, which is the most used substrate for manufacturing pencil-drawn electrodes, the MSLA-3D-printed substrate has the advantages of not absorbing water (hydrophobicity) or becoming crinkled and weakened when in contact with solutions. These features provide more reproducible, reliable, stable, and long-lasting sensors. The MSLA-3D-PDE, in conjunction with the custom cell developed, showed excellent robustness and electrochemical performance similar to that observed of the glassy carbon electrode, without the need of any activation procedure. The analytical applicability of this platform was explored through the quantification of omeprazole in pharmaceuticals. A limit of detection (LOD) of 0.72 µmol L–1 was achieved, with a linear range of 10 to 200 µmol L–1. Analysis of real samples provided results that were highly concordant with those obtained by UV-Vis spectrophotometry (relative error ≤ 1.50%). In addition, the greenness of this approach was evaluated and confirmed by a quantitative methodology (Eco-Scale index). Thus, the MSLA-3D-PDE appears as a new and sustainable tool with great potential of use in analytical electrochemistry. [ABSTRACT FROM AUTHOR]

Electrochemical (EC) detection is a powerful tool supporting simple, low-cost, and rapid analysis. Although screen printing is commonly used to mass fabricate disposable EC chips, its mask is relatively expensive. In this research, we demonstrated a method for fabricating three-electrode EC chips using 3D printing of relatively high-viscosity paste. The electrodes consisted of two layers, with carbon paste printed over silver/silver chloride paste, and the printed EC chips were baked at 70 °C for 1 h. Engineering challenges such as bulging of the tubing, clogging of the nozzle, dripping, and local accumulation of paste were solved by material selection for the tube and nozzle, and process optimization in 3D printing. The EC chips demonstrated good reversibility in redox reactions through cyclic voltammetry tests, and reliably detected heavy metal ions Pb(II) and Cd(II) in solutions using differential pulse anodic stripping voltammetry measurements. The results indicate that by optimizing the 3D printing of paste, EC chips can be obtained by maskless and flexible 3D printing techniques in lieu of screen printing.

The development of surface modification techniques has brought about a major paradigm shift in the clinical applications of bone tissue regeneration. Biofabrication strategies enable the creation of scaffolds with specific microstructural environments and biological components. Lithium (Li) has been reported to exhibit anti-inflammatory, osteogenic, and chondrogenic properties by promoting several intracellular signaling pathways. Currently, research focuses on fabricating scaffolds with simultaneous dual bioactivities to enhance osteochondral regeneration. In this study, we modified the surface of calcium silicate (CS) scaffolds with Li using a simple immersion technique and evaluated their capabilities for bone regeneration. The results showed that Li ions could be easily coated onto the surfaces of CS scaffolds without affecting the microstructural properties of CS itself. Furthermore, the modifications did not affect the printing capabilities of the CS, and porous scaffolds could be fabricated via extrusion. Moreover, the presence of Li improved the surface roughness and hydrophilicity, thus leading to enhanced secretion of osteochondral-related regeneration factors, such as alkaline phosphatase (ALP), bone sialoprotein (BSP), and collagen II (Col II) proteins. Subsequent in vivo studies, including histological and micro-CT analyses, confirmed that the Li-modified CS scaffolds promoted osteochondral regeneration. The transcriptome analysis suggested that the enhanced osteochondrogenic capabilities of our scaffolds were influenced by paracrine exosomes. We hope this study will inspire further research on osteochondral regeneration.

Laser powder bed fusion (LPBF) has unique metal processing characteristics that allow rapid heating and melting of metal powder to form the 3D objects in a layer-by-layer manner. The parts fabricated through LPBF inherited anisotropy behaviors in microstructure and mechanical performance. To effectively ensure the as-built part functionality in terms of microstructure and mechanical performance, scanning direction (SD), building direction (BD), and transverse direction (TD) were selected to be analyzed to build a quantitative process-quality model to control the tensile strength in this study. The influence of hatch distance on microstructure evolution is also investigated. X-ray diffraction (XRD) analysis indicated that (200) peak intensity of γ austenite (fcc) drop-down with hatch distance increased from 0.06 mm to 0.10 mm. Broadening of remelting zone of two adjacent tracks improved the epitaxial growth of column grain. The different ratios of tensile strength and elongation between scanning direction and building direction are 9.23, 19.26% with hatch distance of 0.06 mm, dropped to 3.27, 10.31% with hatch distance of 0.10 mm, respectively. When the hatch distance is over 0.1 mm, the tensile strength and elongation of TD samples drop sharply due to the lack of overlap between molten pools. The different ratio of mechanical anisotropy decreases with hatch distance increases, which also demonstrates that hatch distance can alter the anisotropic of LPBF-ed parts. [ABSTRACT FROM AUTHOR]

Intra-oral stents (including mouth-pieces and bite blocks) can be used to displace adjacent non-involved oral tissue and reduce radiation side effects from radiotherapy treatments for head-and-neck cancer. In this study, a modular and customisable 3D printed intra-oral stent was designed, fabricated and evaluated, to utilise the advantages of the 3D printing process without the interruption of clinical workflow associated with printing time. The stent design used a central mouth-opening and tongue-depressing main piece, with optional cheek displacement pieces in three different sizes, plus an anchor point for moulding silicone to fit individual patients’ teeth. A magnetic resonance imaging (MRI) study of one healthy participant demonstrated the tissue displacement effects of the stent, while providing a best-case indication of its comfort.