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In recent years, additive manufacturing (AM) has played a significant role in various fashion industries, especially the textile and jewelry manufacturing sectors. This review article delves deeply into the wide range of methods and materials used to make intricately designed jewelry fabrication using the additive manufacturing (AM) process. The Laser Powder Bed Fusion (L-PBF) process is examined for its suitability in achieving complex design and structural integrity in jewelry fabrication even with respect to powder metallurgy methods. Moreover, the review explores the use of precious materials, such as gold, silver, copper, platinum, and their alloys in additive manufacturing. Processing precious materials is challenging due to their high reflectivity and thermal conductivity, which results in poor densification and mechanical properties. To address this issue, the review article proposes three different strategies: (i) adding alloying elements, (ii) coating powder particles, and (iii) using low-wavelength lasers (green or blue). Finally, this review examines crucial post-processing techniques to improve surface quality, robustness, and attractiveness. To conclude, this review emphasizes the potential of combining additive manufacturing (AM) with traditional craftsmanship for creating jewelry, exploring the potential future directions and developments in the field of additive manufacturing (AM) for jewelry fabrication.

Rapid solidification techniques, such as gas atomisation, have been widely implemented in metallic alloys/composites to increase solid solubility, avoid or mitigate segregation phenomena, and favour metastable phase formation to enhance performance. Particularly, gas atomisation can enhance the solid solubility of low diffusion coefficient elements like Fe, Ni, Mn, Zr, and Cr in the α-Al matrix, yielding metastable phases. As a result, Al alloys exhibit excellent strength at high temperatures. In this study, the AISI 304L alloy was employed to introduce Fe, Ni, and Cr elements into the AlSi10Mg alloy through gas atomisation, resulting in the formation of two distinct hypereutectic AlFe-based alloys: AlFe9Si8Cr2Ni and AlFe18Si8Cr5Ni2. Gas-atomised alloy powders were separated into different size fractions by sieving and characterised using X-ray diffraction, differential scanning calorimetry, optical microscopy, and scanning electron microscopy. Microstructural analyses revealed dendritic patterns with distinct phases, highlighting the influence of the alloying element content on the solidification processes. Furthermore, a synergic evaluation of the XRD and EDS analysis results allowed the identification of intermetallic phases and their distribution in the two systems.

A20X (Al-Cu-Ag-Mg-TiB2) is a precipitation hardening alloy, recently developed for additive manufacturing processing. Printed parts of A20X alloy are usually post-processed with a long T7 heat treatment for improved mechanical properties with respect to its as-built counterparts. However, in the present investigation, it was demonstrated that T7 might not be the best suitable heat treatment available for A20X alloy. A detailed microstructural characterization of A20X samples processed with laser powder bed fusion and post-processed with T7 was carried out. Microstructural features were analysed in terms of grain size, precipitate size, phase quantification, dislocation density and width of the precipitate free zones. After the analysis, a simple and rapid heat treatment was proposed which significantly improved the mechanical properties. The yield strength (YS), ultimate tensile strength (UTS) and elongation to fracture (e) for the T7 heat treatment were 370 ± 9 MPa, 435 ± 13 MPa and 7.3 ± 0.3 % respectively. With the proposed heat treatment, an increment of 7.1 % in YS, 6.3 % in UTS and 45 % in e was witnessed. This exceptional improvement in the mechanical behaviour has been associated with the absence of grain boundary cracking in the proposed heat treatment.

Over the past few years, several studies have been conducted on the development of Al-Si-Cu-Mg alloys for PBF-LB/M processing. The attention gained by these systems can be attributed to their light weight and strength provided by a solid solution in the as-built state and by precipitation after heat treatment. However, published studies have kept the copper content below its solubility limit in the Al-Cu binary system under equilibrium conditions (5.65 wt%). The present study aims to explore Al-Si-Cu-Mg systems with high copper content, starting with the well-known AlSi10Cu4Mg system, moving towards AlSi10Cu8Mg, and arriving at AlCu20Si10Mg, a system never before processed with PBF-LB/M. Through the SST approach, the production of bulk samples, advanced microstructural characterization by SEM and FESEM analysis, phase identification by XRD analysis, and preliminary investigation of the mechanical properties through Vickers micro indentations, the effects of copper quantities on the processability, microstructural properties, and mechanical behavior of these compositions were investigated. The obtained results demonstrated the benefits of the supersaturated solid solution and the fine precipitation resulting from the addition of high Cu contents. In particular, the AlCu20Si10Mg system showed a very distinctive microstructure and unprecedented microhardness values.

Inconel 625 (IN625) superalloys can be easily fabricated by the laser-based powder bed fusion (PBF-LB/M) process, allowing the production of components with a high level of design freedom. However, one of the main drawbacks of the PBF-LB/M process is the control over thermally induced stresses and their mitigation. A standard approach to prevent distortion caused by residual stress is performing a stress-relieving (SR) heat treatment before cutting the parts from the building platform. Differently from the cast or wrought alloy, in additively manufactured IN625, the standard SR at 870 °C provokes the early formation of the undesirable δ phase. Therefore, this unsuitable precipitation observed in the PBF-LB/M material drives the attention to develop a tailored SR treatment to minimise the presence of undesirable phases. This work investigates SR at lower temperatures by simultaneously considering their effects on residual stress mitigation, microstructural evolution, and mechanical properties. A multiscale approach with cantilever and X-ray technologies was used to investigate how the residual stress level is affected by SR temperature. Moreover, microstructural analyses and phase identifications were performed by SEM, XRD, EBSD, and DSC analyses. Finally, mechanical investigations through microhardness and tensile tests were performed as well. The results revealed that for the additively manufactured IN625 parts, an alternative SR treatment able to mitigate the residual stresses without a massive formation of δ phase could be performed in a temperature range between 750 and 800 °C.

The Ti-6Al-2Sn-4Zr-6Mo alloy was recently successfully processed using the laser powder bed fusion technology. This material is characterized by a very low strength in the as-built state, due to the presence of α” martensite. In this work, the transformations taking place at different temperatures in this alloy were investigated with the aim of achieving the necessary knowledge to customize the mechanical properties via heat treatments. Martensite decomposition, residual stress relaxation and the β-transus temperature were identified at progressively increasing temperatures. Then, different annealing treatments, corresponding to the temperatures identified, were conducted. For each condition, dissimilar α + β microstructures were obtained, varying in terms of morphology (lamellar, bi-lamellar) and size of the α laths (0.5–2.2 µm). The corresponding tensile properties were also significantly different. In particular, outstanding strength values were achieved when the residual stress was retained. For higher temperatures, a slight drop in strength was coupled with an outstanding improvement in terms of ductility. Overall, the most balanced combination of tensile properties was obtained for an annealing temperature of 875 °C. In this condition, the bi-lamellar microstructure grants a reduction in the slip length due to the presence of secondary α laths.

In this work, a high strength Al alloy was successfully processed via in-situ alloying of AlSi10Mg and Cu elemental powders during Laser Powder Bed Fusion. To get superior strength, 4 wt% of Cu was added to AlSi10Mg composition to benefit from the additional solid solution and precipitation strengthening mechanisms induced by Cu atoms. Microstructure, chemical composition, hardness, and tensile properties of as-built samples were firstly determined. The microstructure showed a dual eutectic formed by Si precipitates intermixed with θ-Al2Cu phase. The average Cu concentration was 3.96 ± 0.26 wt% in line with the theoretical one. Hardness and yield strength of AlSi10Mg + 4Cu alloy showed an increase of respectively 8.8 % and 35.6 % compared to the as-built AlSi10Mg, owing to the highly super-saturated solid solution of Si and Cu atoms upon rapid solidification. After that, a direct aging heat-treatment strategy was pursued to fully exploit the potential alloy precipitation by heating as-built samples at temperatures between 160 and 190 °C. A maximum hardness response was achieved after 1 h at 175 °C. The high hardening was primarily attributed to a mix of θ''/θ'+θ-Al2Cu and Si phases coupled with a still high solid solution content. Nevertheless, direct aging slightly decreased the alloy ductility due to the prominent precipitation of brittle Si particles during aging and the presence of Cu inhomogeneities formed after in-situ alloying.

Among the recently developed compositions tailored for the power bed fusion-laser beam process (PBF-LB), the novel Al-Mn-Cr-Zr alloy stands out. This composition exploits high solid solution strengthening, achieving a high hardness value in the as-built condition. The produced samples are inherently crack-free and have a good level of densification (~99.5%). The goal of this study is to investigate how this quaternary system is affected by the laser power while retaining a similar volumetric energy density. A comparison between the microstructural features and the mechanical performance was performed on a set of samples processed with power values ranging from 100 to 170 W. Microstructural features were investigated through optical microscopy, Electron Back Scattered Diffraction (EBSD) investigation and feature analysis using advanced microscopy to examine the amount, distribution, and shape of precipitates in the different process conditions. Although the quantitative feature analysis permitted analysis of more than 60 k precipitates for each power condition, all samples demonstrated a low level of precipitation (below 0.3%) with nanometric size (around 75 nm). The mechanical performances of this quaternary system as a function of the laser power value were evaluated with a microhardness test, recording very similar values for the different process conditions with a mean value of approximately 104 HV. The results suggested a very stable system over the tested range of process parameters. In addition, considering the low level of precipitation of nanometric phases enriched in Al-Mn, a supersaturated state could be established in each process condition.

Metal parts produced by Additive Manufacturing, and in particular Laser Powder Bed Fusion (LPBF), suffer from residual stresses due to high thermal gradients causing cyclic expansion and contraction of the alloy.This work deals with the determination of residual stress in rapidly solidified AlSi10Mg samples using two non-destructive techniques: Raman spectroscopy, rapid, unconventional but applicable to AlSi alloys, and XRD (ω-method), used as benchmark, being a classical method for determining residual stresses. Al stress level was studied by XRD both on the surface of LPBF samples and in the interior, after in-depth sectioning. Raman was employed to assess the stress on Si. The effect of particle size and stress on the Raman was separated determining the size distribution of Si particles, making Raman suitable to study residual stresses in alloys containing free Si.Al and Si stresses were evaluated also by means of the Williamson-Hall method: stresses are of tensile type with agreement among all methods. Considering the alloy as a composite, stress on Si was estimated using the Eshelby's model, showing that larger eutectic particles undergo lower stress with respect to nanometric precipitates.

Myopericytoma is a benign neoplasm presenting cells with different shapes, from oval to spindle, and myoid showing with perivascular growth, which frequently originates from the skin and soft tissues of distal extremities, trunk, head, and neck regions. These tumors rarely have been reported to occur in visceral sites. There is only one case of myopericytoma showing pulmonary involvement with multiple nodules. Although most myopericytomas behave in a benign manner, some cases of malignant myopericytoma arising in both superficial soft tissue and visceral locations have been described. We describe two cases of pulmonary tumors with myopericytoma-like features.

Definition of the main process parameters, laser power (P), scanning speed (v), hatching distance (hd) and scanning strategy useful for producing dense samples, is fundamental to develop novel alloy compositions for Laser Powder Bed Fusion (LPBF). The present work has two aims: on one side, to verify the processability of a new AlSi10Mg + 4Cu alloy of mixed powders by LBPF; on the other side, on the basis of the experimental analysis, to define a method for processing new alloys. Producing Single Scan Tracks (SSTs), samples with unidirectional scanning strategy and samples with 67° rotated scanning strategy, the proper P-v-hd combinations were identified reaching a final porosity lower than 1.5%. A scenario of hardness and build-up rate vs. energy density is given, to adopt the main process parameters suitable to maximize mechanical properties or productivity. According to the novel method, P-v-hd combinations can be defined through the production and characterization of SSTs and samples with 67° rotated scanning strategy. Through two production steps dense samples can be then obtained, allowing the development of new compositions saving time and reducing costs related to the powder usage. Keywords: Laser Powder Bed Fusion (LPBF), Single scan tracks (SSTs), Hatching distance (hd), Overlap, Process parameters, Hardness, Build-up rate

This work aims to investigate the effect of the process parameters on the densification and microstructure of Inconel 939 (IN939) alloy processed by laser powder bed fusion (LPBF). IN939 is a Ni-based superalloy with high creep and corrosion resistance that can be used up to around 850 °C under load, resulting in higher operative temperatures than the ones commonly allowed for Inconel 718 and Inconel 625 alloys (around 650 °C). However, this alloy can suffer from poor weldability involving possible crack formation. In order to minimize the residual porosity and the cracking density, specific process parameters were investigated. The parameters to generate IN939 samples almost pores-free (porosity ≤0.22%) with a cracking density ≤1.36 mm/mm2 as well as samples almost crack-free (≤0.10 mm/mm2) with limited residual porosity (≤0.89%) were determined. The microstructure revealed fine dendritic/cellular structures with the formation of sub-micrometric phases. A high concentration of these phases was also found along the intergranular cracks, suggesting that their presence, coupled to the high thermal stresses, can be the primary reason for crack formation during the LPBF process.

Blown powder additive manufacturing technologies are not restricted to the use of a process chamber. This feature allows to build larger components with respect to conventional powder bed processes. This peculiarity is mostly promising for manufacturing large components or repairing/rebuilding parts of large systems. The main downside of using an open environment, even if a protective shielding gas system is adopted, is the lack of control of process atmosphere. This is particularly critical for titanium alloys which are very sensitive to oxygen/nitrogen pick-up; they have a detrimental effect on ductility, by causing embrittlement and possibly leading to the formation of cracks. It is then important to address how environmental factors, such as process atmosphere and platform temperature, impact not only on the processability but also on the final component properties, both from a compositional and mechanical point of view. The correlations between these environmental factors and microstructure, interstitials content, grain size, and hardness were investigated. Moreover, the Hall–Petch equation was then adopted to additive manufacturing microstructures, characterized by a columnar grain morphology, and used to further investigate the relationship intercurring between grains and hardness and how different microstructures might influence this correlation.

Directed energy deposition (DED) as a metal additive manufacturing technology can be used to produce or repair complex shape parts in a layer-wise process using powder or wire. Thanks to its advantages in the fabrication of net-shape and functionally graded components, DED could attract significant interest in the production of high-value parts for different engineering applications. Nevertheless, the industrialization of this technology remains challenging, mainly because of the lack of knowledge regarding the microstructure and mechanical characteristics of as-built parts, as well as the trustworthiness/durability of engineering parts produced by the DED process. Hence, this paper reviews the published data about the microstructure and mechanical performance of DED AISI 316L stainless steel. The data show that building conditions play key roles in the determination of the microstructure and mechanical characteristics of the final components produced via DED. Moreover, this review article sheds light on the major advancements and challenges in the production of AISI 316L parts by the DED process. In addition, it is found that in spite of different investigations carried out on the optimization of process parameters, further research efforts into the production of AISI 316L components via DED technology is required.

Post-processing treatments of metallic materials play a key role in the achievement of high mechanical and surface properties of the final components and in the optimization of their behavior in service conditions [...]

In blown powder additive manufacturing technologies the geometrical stability of the built parts is more complex with respect to more conventional powder bed processes. Because of this reason, in order to select the most suitable building parameters, it is important to investigate the shape and the properties of the single metal bead formation and the effect that a scan track has on the nearby ones. In the present study, a methodology to identify an appropriate laser metal deposition process window was introduced, and the effect of the building parameters on the geometry of circular steel samples was investigated. The effect of the scanning strategy on the deposited part was also investigated. This work draws the attention to the importance of the obtainment of the most suitable melt pool shape, demonstrating that the laser power and the scanning strategy have a strong influence not only on the shape but also on the mechanical properties of the final component.

In the circular economy, products, components, and materials are aimed to be kept at the utility and value all the lifetime. For this purpose, repair and remanufacturing are highly considered as proper techniques to return the value of the product during its life. Directed Energy Deposition (DED) is a very flexible type of additive manufacturing (AM), and among the AM techniques, it is most suitable for repairing and remanufacturing automotive and aerospace components. Its application allows damaged component to be repaired, and material lost in service to be replaced to restore the part to its original shape. In the past, tungsten inert gas welding was used as the main repair method. However, its heat affected zone is larger, and the quality is inferior. In comparison with the conventional welding processes, repair via DED has more advantages, including lower heat input, warpage and distortion, higher cooling rate, lower dilution rate, excellent metallurgical bonding between the deposited layers, high precision, and suitability for full automation. Hence, the proposed repairing method based on DED appears to be a capable method of repairing. Therefore, the focus of this study was to present an overview of the DED process and its role in the repairing of metallic components. The outcomes of this study confirm the significant capability of DED process as a repair and remanufacturing technology.

Al-Si-Zn-Mg-Cu samples were produced using Laser Powder Bed Fusion from mixed AlSi10Mg and 7075 powders. It was observed that the introduction of silicon to an Al-Zn-Mg-Cu alloy strongly reduced the crack density, probably because of the reduction of the solidification range, the improved fluidity of the molten phase and the reduction of the coefficient of thermal expansion. The density measurements showed that crack-free samples can be successfully produced with this powder mixture. The obtained Al-Si-Zn-Mg-Cu samples were characterized in terms of microstructure, hardness and tensile properties showing that this composition is very promising for future powder bed additive manufacturing processes.

Recently, additive manufacturing techniques have been gaining attention for the fabrication of parts from aluminium alloys to composites. In this work, the processing of an AlSi10Mg based composite reinforced with 0.5% in weight of MgAl2O4 nanoparticles through laser powder bed fusion (LPBF) process is presented. After an initial investigation about the effect of process parameters on the densification levels, the LPBF materials were analysed in terms of microstructure, thermo-mechanical and mechanical properties. The presence of MgAl2O4 nanoparticles involves an increment of the volumetric energy density delivered to the materials, in order to fabricate samples with high densification levels similar to the AlSi10Mg samples. However, the application of different building parameters results in modifying the size of the cellular structures influencing the mechanical properties and therefore, limiting the strengthening effect of the reinforcement.

Background. The purpose of this study was to compare the accuracy of whole-body MRI with diffusion-weighted sequences (WB-DW-MRI) with that of 18F-FDG-PET/CT in the staging of patients with primary gastrointestinal lymphoma. Methods. This retrospective study involved 17 untreated patients with primary abdominal gastrointestinal lymphoma. All patients underwent 18F-FDG-PET/CT and WB-DW-MRI. Histopathology findings or at least 6 months of clinical and radiological follow-up was the gold standard. The Musshoff-modified Ann Arbor system was used for staging, and diagnostic accuracy was evaluated on a per-node basis. Results. WB-DW-MRI exhibited 100% sensitivity, 96.3% specificity, and 96.1% and 100% positive and negative predictive values (PPV and NPV), respectively. The sensitivity, specificity, and PPV and NPV of PET/CT were 95.9%, 100%, and 100% and 96.4%, respectively. There were no statistically significant differences between the two techniques p=0.05. The weighted kappa agreement statistics with a 95% confidence interval were 0.97 (0.95–0.99) between the two MRI readers and 0.87 (0.82–0.92) between the two methods. Conclusions. WB-DW-MRI appears to have a comparable diagnostic value to 18F-FDG-PET/CT in staging patients with gastrointestinal lymphoma.

The directed energy deposition (DED) process can be employed to build net shape components or prototypes starting from powder or wires, through a layer-by-layer process. This process provides an opportunity to fabricate complex shaped and functionally graded parts that can be utilized in different engineering applications. DED uses a laser as a focused heat source to melt the in-situ delivered powder or wire-shaped raw materials. In the past years extensive studies on DED have shown that this process has great potential in order to be used for (i) rapid prototyping of metallic parts, (ii) fabrication of complex and customized parts, (iii) repairing/cladding valuable components which cannot be repaired by other traditional techniques. However, the industrial adoption of this process is still challenging owing to the lack of knowledge on the mechanical performances of the constructed components and also on the trustworthiness/durability of engineering parts produced by DED. This manuscript provides an overview of the additive manufacturing (AM) of titanium alloys and focuses in particular on the mechanical properties and microstructure of components fabricated by DED.

Anti-ice systems assure a vital on-board function in most aircraft: ice prevention or de-icing is mandatory for all aerodynamic surfaces to preserve their performance, and for all the movable surfaces to allow the proper control of the plane. In this work, a novel multi-functional panel concept which integrates anti-icing directly inside the primary structure is presented. In fact, constructing the core of the sandwich with trabecular non-stochastic cells allows the presence of a heat exchanger directly inside the structure with a savings in weight and an improvement in thermal efficiency. This solution can be realized easily in a single-piece component using Additive Manufacturing (AM) technology without the need for joints, gluing, or welding. The objective of this study is to preliminarily investigate the mechanical properties of the core constructed with Selective Laser Melting (SLM); through the Design of Experiment (DOE), different design parameters were varied to understand how they affect the compression behaviour.

Abstract: In order to improve the process efficiency of a direct energy deposition (DED) system, closed loop control systems can be considered for monitoring the deposition and melting processes and adjusting the process parameters in real-time. In this paper, the monitoring of a new deposition nozzle solution for DED systems is approached through a simulation-experimental comparison. The shape of the powder flow at the exit of the nozzle outlet and the spread of the powder particles on the deposition plane are analyzed through 2D images of the powder flow obtained by monitoring the powder depositions with a high-speed camera. These experimental results are then compared with data obtained through a Computational Fluid Dynamics model. Preliminary tests are carried out by varying powder, carrier, and shielding mass flow, demonstrating that the last parameter has a significant influence on the powder distribution and powder flow geometry.

A357 samples were realized by laser powder bed fusion (LPBF) on building platforms heated up to different temperatures. The effect of the preheating temperature and of the post processing heat treatment on the microstructure and the mechanical properties of the samples was studied. It was demonstrated that building platform heating can act as an in situ ageing heat treatment following the fast cooling that arises during laser scanning. A 17% higher ultimate tensile strength was achieved by the selection of the optimum building platform temperature. Moreover, the possibility to further increase the mechanical properties by means of a direct ageing heat treatment was investigated.

Recently, diffuse-large-B-cell lymphoma (DLBCL) associated with serum IgM monoclonal component (MC) has been shown to be a very poor prognostic subset although, detailed pathological and molecular data are still lacking. In the present study, the clinicopathological features and survival of IgM-secreting DLBCL were analyzed and compared to non-secreting cases in a series of 151 conventional DLBCL treated with R-CHOP. IgM MC was detected in 19 (12.5%) out of 151 patients at disease onset. In 17 of these cases secretion was likely due to the neoplastic clone, as suggested by the expression of heavy chain IgM protein in the cytoplasm of tumor cells. In IgM-secreting cases immunoblastic features (p