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Binder jetting is a promising route to produce complex copper components for electronic/thermal applications. This paper aims to lay a framework for determining the effects of sintering parameters on the final microstructure of copper parts fabricated through binder jetting.

The knowledge gained from well-established powder metallurgy processes was leveraged to study the densification behaviour of a fine high-purity copper powder (D₅₀ of 3.4 µm) processed via binder jetting, by performing dilatometry and microstructural characterization. The effects of sintering parameters on densification of samples obtained with a commercial water-based binder were also explored.

Sintering started at lower temperature in cold-pressed (∼680 °C) than in binder jetted parts (∼900 °C), because the strain energy introduced by powder compression reduces the sintering activation energy. Vacuum sintering promoted pore closure, resulting in greater and more uniform densification than sintering in argon, as argon pressure stabilizes the residual porosity. About 6.9% residual porosity was obtained with air sintering in the presence of graphite, promoting solid-state diffusion by copper oxide reduction.

This paper reports the first systematic characterization of the thermal events occurring during solid-state sintering of high-purity copper under different atmospheres. The results can be used to optimize the sintering parameters for the manufacturing of complex copper components through binder jetting.

This paper aims to investigate the structure and scratch resistance properties of gas nitrided pure iron samples.

The effects of material strain hardening and amount of grain boundaries exposed on nitriding surface were evaluated by cold rolling the starting samples to different reduction levels before gas nitriding.

The study finds that nitriding without any prior cold rolling produced a comparatively wide compound layer with a large fraction of porous zone featuring low scratch hardness values but no evidence of damage. On the contrary, cold rolling before nitriding led to a more irregular and thinner compound layer with reduced amount of porous zone and much finer nitrides in the diffusion zone. Scratch hardness was increased but failure mechanism changed by generation of conformal cracks within the track groove and the appearance of discontinuous spallation at high loads.

One of the issues of great industrial importance concerning nitriding of steels is the need to predict the extent of the nitrided layer in products showing small variations in microstructure or in extent of cold working due to complex manufacturing cycles. Despite the practical importance, relatively little information is available in literature about these issues. The present paper is therefore aimed at investigating the structure and mechanical properties of pure iron samples, gas nitrided with different amounts of cold working and microstructural conditions.

In binder jetting, the interaction between the liquid binder droplets and the powder particles defines the shape of the printed primitives. The purpose of this study is to explore the interaction of the relative size of powder particles and binder droplets and the subsequent effects on macro-scale part properties.

The effects of different particle size distribution (5–25 µm and 15–45 µm) of stainless steel 316 L powders and droplet sizes (10 and 30 pL) on part density, shrinkage, mechanical strength, pore morphology and distribution are investigated. Experimental samples were fabricated in two different layer thicknesses (50 and 100 µm).

While 15–45 µm samples demonstrated higher green density (53.10 ± 0.25%) than 5–25 µm samples (50.31 ± 1.06%), higher sintered densities were achieved in 5–25 µm samples (70.60 ± 6.18%) compared to 15–45 µm samples (65.23 ± 3.24%). Samples of 5–25 µm also demonstrated superior ultimate tensile strength (94.66 ± 25.92 MPa) compared to 15–45 µm samples (39.34 ± 7.33 MPa). Droplet size effects were found to be negligible on both green and sintered densities; however, specimens printed with 10-pL droplets had higher ultimate tensile strength (79.70 ± 42.31 MPa) compared to those made from 30-pL droplets (54.29 ± 23.35 MPa).

To the best of the authors’ knowledge, this paper details the first report of the combined effects of different particle size distribution with different binder droplet sizes on the part macro-scale properties. The results can inform appropriate process parameters to achieve desired final part properties.

Material extrusion (ME) is a low-cost additive manufacturing (AM) technique that is capable of producing metallic components using desktop 3D printers through a three-step printing, debinding and sintering process to obtain fully dense metallic parts. However, research on ME AM, specifically fused filament fabrication (FFF) of 316L SS, has mainly focused on improving densification and mechanical properties during the post-printing stage; sintering parameters. Therefore, this study aims to investigate the effect of varying processing parameters during the initial printing stage, specifically nozzle temperatures, T_n (190°C–300°C) on the relative density, porosity, microstructures and microhardness of FFF 3D printed 316L SS.

Cube samples (25 x 25 x 25 mm) are printed via a low-cost Artillery Sidewinder X1 3D printer using a 316L SS filament comprising of metal-polymer binder mix by varying nozzle temperatures from 190 to 300°C. All samples are subjected to thermal debinding and sintering processes. The relative density of the sintered parts is determined based on the Archimedes Principle. Microscopy and analytical methods are conducted to evaluate the microstructures and phase compositions. Vickers microhardness (HV) measurements are used to assess the mechanical property. Finally, the correlation between relative density, microstructures and hardness is also reported.

The results from this study suggest a suitable temperature range of 195°C–205°C for the successful printing of 316L SS green parts with high dimensional accuracy. On the other hand, T_n = 200°C yields the highest relative density (97.6%) and highest hardness (292HV) in the sintered part, owing to the lowest porosity content (<3%) and the combination of the finest average grain size (∼47 µm) and the presence of Cr23C6 precipitates. However, increasing T_n = 205°C results in increased porosity percentage and grain coarsening, thereby reducing the HV values. Overall, these outcomes suggest that the microstructures and properties of sintered 316L SS parts fabricated by FFF AM could be significantly influenced even by adjusting the processing parameters during the initial printing stage only.

This paper addresses the gap by investigating the impact of initial FFF 3D printing parameters, particularly nozzle temperature, on the microstructures and physical characteristics of sintered FFF 316L SS parts. This study provides an understanding of the correlation between nozzle temperature and various factors such as dimensional integrity, densification level, microstructure and hardness of the fabricated parts.

This study aims at compensating for sintering deformation of components manufactured by metal binder jetting (MBJ) technology.

In the present research, numerical simulations are used to predict sintering deformation. Subsequently, an algorithm is developed to counteract the deformations, and the compensated deformations are morphed into a CAD model for printing. Several test cases are designed, compensated and manufactured to evaluate the accuracy of the compensation calculations. A consistent accuracy measurement method is developed for both green and sintered parts. The final sintered parts are compared with the desired final shape, and the accuracy of the model is discussed. Furthermore, the effect of initial assumptions in the calculations, including green part densities, and green part dimensions on the final dimensional accuracy are studied.

The proposed computational framework can compensate for the sintering deformations with acceptable accuracy, especially in the directions, for which the used material model has been calibrated. The precise assumption of green part density values is important for the accuracy of compensation calculations. For achieving tighter dimensional accuracy, green part dimensions should be incorporated into the computational framework.

Several studies have already predicted sintering deformations using numerical methods for MBJ parts. However, very little research has been dedicated to the compensation of sintering deformations with numerical simulations, and to the best of the best of the authors' knowledge, no previous work has studied the effect of green part properties on dimensional accuracy of compensation calculations. This paper introduces a method to omit or minimize the trial-and-error experiments and leads to the manufacturing of dimensionally accurate geometries.

Somalia is an East African nation with a history of civil unrest that produced a significant influx of refugees in the USA in the last 25 years. Between 2000 and 2010, 40 percent of all US Somali refugees settled in Minnesota, which produces new cultural and health challenges for local communities and the state government. One such challenge is vitamin D deficiency, or hypovitaminosis D (Hv-D). Hv-D is developed through insufficient exposure to sunlight and low nutrient intake leading to increased risk for weakness and inflammation, oral health problems, diabetes, cardiovascular and autoimmune diseases and malignancies. The paper aims to discuss these issues.

In this narrative review, demographic, geographic and cultural information about Somali immigration are discussed.

Recent data suggest Somalis living in northern climates (Minnesota, the USA, Helsinki, Finland, Sweden and the UK) experience significant deficiencies in vitamin D. Vitamin D is stimulated by ultraviolet light exposure, a balanced and healthy diet, and dietary supplementation. High unemployment rates affecting access to health information and clinical services, significant cultural differences and climate differences pre-dispose this population to Hv-D. Health education and health promotion programming at the community and state levels in Minnesota should recognize the risk factors associated with Hv-D and the vulnerability of Somali refugees.

Current and future health programming should be re-assessed for adequate attention to vitamin D deficiency and cultural competency associated with the Somali immigrant population.

The use of additive manufacturing in many branches of industry is increasing significantly because of its many advantages, such as being able to produce complex parts that cannot be produced by classical methods, using fewer materials, easing the supply chain with on-site production, being able to produce with all kinds of materials and producing lighter parts. The binder jetting technique, one of the additive manufacturing methods researched within the scope of this work, is predicted to be the additive manufacturing method that will grow the most in the next decade, according to many economic reports. Although additive manufacturing methods have many advantages, they can be slower than classical manufacturing methods regarding production speed. For this reason, this study aims to increase the manufacturing speed in the binder jetting method.

Adaptive slicing and variable binder amount algorithm (VBAA) were used to increase manufacturing speed in binder jetting. Taguchi method was used to optimize the layer thickness and saturation ratio in VBAA. According to the Taguchi experimental design, 27 samples were produced in nine different conditions, three replicates each. The width of the samples in their raw form was measured. Afterward, the samples were sintered at 1,500 °C for 2 h. After sintering, surface roughness and density tests were performed. Therefore, the methods used have been proven to be successful. In addition, measurement possibilities with image processing were investigated to make surface roughness measurements more accessible and more economical.

As a result of the tests, the optimum printing condition was decided to be 180–250 µm for layer thickness and 50% for saturation. A separate test sample was then designed to implement adaptive slicing. This test sample was produced in three pieces: adaptive (180–250 µm), thin layer (180 µm) and thick layer (250 µm) with the determined parameters. The roughness values of the adaptive sliced sample and the thin layer sample were similar and better than the thick layer sample. A similar result was obtained using 12.31% fewer layers in the adaptive sample than in the thin layer sample.

The use of adaptive slicing in binder jetting has become more efficient. In this way, it will increase the use of adaptive slicing in binder jetting. In addition, a cheap and straightforward image processing method has been developed to calculate the surface roughness of the parts.

This paper aims to evaluate the efficacy of a zeolite-filled silane sol–gel coating as protective layer on pretreated AZ31 magnesium alloy substrates.

Anti-corrosion properties of a silane–zeolite composite coating, at various zeolite content, have been investigated on AZ31 magnesium substrates subjected to different surface pretreatment procedures before coating deposition. A short time etching by hydrofluoric acid (HF) and an anodic polarization in NaOH solution were used as surface pretreatments.

High hydrophobicity and good adhesion performances of coatings have been observed. Corrosion protection performance, during immersion in 3.5 per cent NaCl solution, was evaluated by means of electrochemical impedance spectroscopy tests. All coating formulations evidenced good barrier properties. Better durability properties have been shown by coating obtained on HF pretreated magnesium substrate and with a 60 per cent of zeolite content.

High electrochemical reactivity of magnesium alloys represents the mayor limit of its application in many different fields. In this concern, zeolite-based coatings are emerging as potentially effective environmentally friendly coating for metallic substrates. Despite aluminum and stainless steel substrates, in the literature, only expensive direct synthesis zeolite coating was investigated for its application on magnesium alloys protection. For this reason, this paper fulfills the need to assess the adhesion and anti-corrosion behavior of sol–gel silane–zeolite coating in magnesium alloy substrates.

This paper aims to establish the microstructures and the process-structure relationships in duplex stainless steel powders consolidated by selective laser melting (SLM).

A priori data on energy density levels most appropriate to consolidation of duplex stainless steel powders through SLM served as the basis to converge on the laser settings. Experimental designs with varying laser power and scan speeds and test pieces generated allowed metallographic evaluations based on optical and scanning electron microscopy and electro backscatter diffraction analyses.

Duplex stainless steel powders are established for processing by SLM. However, the dynamic point heat source and associated transient thermal fields affect the microstructures to be predominantly ferritic, with grains elongated in the build direction. Austenite precipitated either at the grain boundaries or as Widmanstätten laths, whereas the crystallographic orientations and the grain growth are affected around the cavities. Considerable CrN precipitation is also evidenced.

Duplex stainless steels are relatively new candidates to be brought into the additive manufacturing realm. Considering the poor machinability and other difficulties, the overarching result indicating suitability of duplex powders by SLM is of considerable value to the industry. More significantly, the metallographic evaluation and results of the current research allowed further understanding of the material consolidation aspects and pave ways for fine tuning and establishment of the process-structure-property relationships for this important process-material combination.

This study aims to further the understanding of support structures and the likely impacts on maraging steel MS1 parts fabricated by selective laser melting (SLM) at 45°, 60° and 75° building angles.

Two groups of samples, one group with support structures and the other group without support structures, were designed with the same specifications and printed under the same conditions by SLM at 45°, 60° and 75° building angles. Differences in dimensional accuracy, surface roughness, Vickers microhardness, residual stress and microstructure were compared between groups.

The results showed that with support structures, more accurate dimension and slightly higher Vickers microhardness could be obtained. Larger compressive stress dominated and was more uniformly distributed on the supporting surface. Without support structures, the dimension became more precise as the building angle increased and alternating compressive and tensile stress was unevenly distributed on the supporting surface. In addition, the surface roughness of the outer surface decreased with the increase of the built angle, regardless of the support structures. Furthermore, whether the building angle was 45°, 60° or 75°, the observed microstructures revealed that the support structures altered the orientation of the molten pool and the direction of grain growth.

This paper studies the influence of support structures on the workpieces printed at different building angles. Support structures affect the residual stress distribution, heat dissipation rate and microstructure of the parts, and thus affecting the printing quality. Therefore, it is necessary to balance the support strategy and printing quality to better apply or design the support structures in SLM.