Among high-strength materials tailored for Powder Bed Fusion - Laser Based, aluminum alloys have gained great relevance. The addition of specific elements can significantly increase the strength via precipitation hardening, solid solution and grain refinement. One of the most successful alloy solutions are the 5xxx series alloys (i.e., Al-Mg), with Sc and Zr. During the solidification, these elements generate Al3(Sc,Zr) nano particles that act as nucleation sites for grain refinement and provide great thermal stability. Because of high yield strength, ultimate tensile strength and good elongation, these materials are ideal for high-demanding applications. Commercial examples of available Al-Mg-Sc-Zr materials include StrengthAl. In basic physics research experiments, vacuum environments along with low and high temperatures are often present to reduce the influence of the outside world or to reproduce and study specific phenomena. Consequently, the development of system and components involves the use of high-performance materials and manufacturing techniques that can meet all design constraints. However, these high-demanding operating conditions need a careful characterization of material properties. Thus, the aim of the paper is to investigate the mechanical behavior of the StrengthAl at different temperatures, such as -100 °C, +22 °C, +100 °C and +200 °C. Average tensile properties, like elastic modulus, Poisson ratio, yield strength, ultimate tensile strength and elongation have been determined as temperature changes. The results highlighted the operational limits of the material in the range of ±100 °C, where it still possesses high strength and stability, due to the presence of Al3(Sc,Zr) nano particles.

Additive Manufacturing allows the fabrication of complex shape parts, but the manufacturing processes may introduce defects that undermine the mechanical performance. In the presented study, the influence of selected process parameters and testing conditions on the fatigue life of Ti6Al4V alloys produced by Electron Beam-Powder Bed Fusion (EB-PBF) has been studied. To study the effects of process parameters, the EB-PBF machine was operated in manual mode, bypassing proprietary manufacturing algorithms. Moreover, various load ratios were considered for fatigue tests conducted under constant-amplitude loads. The results established a direct relationship between energy density, microstructure, and fatigue resistance. It was found that the beam current and the scan speed significantly determined the energy density of the process and, consequently, the material porosity and density, so affecting the mechanical performance. These findings indicate that careful selection and control of manufacturing parameters can enhance fatigue properties in EB-PBF components. This information can be used to support the development of AI-based optimisation strategies to predict stress-related behaviour and minimise defects, such as cracking and residual stress.

Powder Bed Fusion-Laser-Based (PBF-LB) technology is widely employed in many fields, but specific highly demanding applications, such as multi-materials (MM), are still not fully investigated. In basic-physics research, experiments operate under extreme conditions to reduce external influences on detectors and to achieve high interaction energies between particles. The opportunity to combine different materials could allow the development of new highly customized components, where the physical properties gradually change along the three directions (x, y, z). Among components that can benefit from this last MM production, there are target holders, beam stops, and target backings. These components must withstand high temperatures and strong thermal gradients without being damaged. All of them must be as transparent as possible to the radiation emitted in the nuclear reactions of interest on its way to the detectors, but beam stops and backings must also be able to stop the beam. High-density or refractory materials, such as tungsten (W) and tantalum, can be used to stop the beam or as target backings. The aim of the paper is experimental characterization of a MM junction between Glenn Research Center Copper (GRCop42) alloy and pure W, produced by PBF-LB technology, for the design of a particle accelerator target assembly. In particular, the 12C+12C fusion reaction measurement case study of the Laboratory for Underground Nuclear Astrophysics has been considered. The MM junction has been characterized by metallographic analyses and three point bending tests, from room temperature to +300 degrees C. GRCop42 alloy has been selected for its excellent thermal properties, great creep resistance, and strength at high temperatures, while pure W has been selected for its high atomic number, which prevents parasitic reactions on the beam stop. The results show that although W is difficult to process with an ordinary PBF-LB machine because of the high presence of porosity and internal defects, the presence of a thin layer of W on a GRCop42 substrate changes the strain behavior compared to GRCop42 alone. For instance, deformation is less influenced by high temperatures. Furthermore, while the GRCop42-W junction is less continuous than in other MM examples, it still allows sufficient W deposition to completely stop the ion beam.

Additive Manufacturing (AM) technology is one of the most promising processes for the production of complex shape parts. A number of issues still remain unsolved, among which the fundamental one is the definition of a model able to predict the mechanical behavior of additively manufactured components starting from the knowledge of the alloy microstructure and the process-induced defects. Ongoing research aims at optimizing the use of AM technologies in several industrial fields, like medical, aerospace and mechanical. This goal requires in-depth characterization of the alloy microstructure and of the metallurgical defects in terms of morphology and distribution, the determination of mechanical properties of AM-produced specimens (like fatigue of materials, fatigue damage, fracture toughness,…), and the development of a predictive model based on artificial intelligence (AI) algorithms. The first step requires the ability of classifying images obtained from specimens produced with different process parameters and, consequently, presenting various mechanical properties. In this paper, this goal is pursued by means of a totally automatized procedure based on advanced methods of machine learning (ML); the first results, obtained on real specimens fabricated using Electron Beam Powder Bed Fusion (EB-PBF), are promising, showing the classifier ability of obtaining satisfactory results after a training on limited number of images.

The CuCrZr alloy has garnered significant interest as a promising material for additive manufacturing, particularly in applications requiring high strain rate performance. Such applications include vertical targets like heat sinks in the ITER divertor and actively cooled plasma-facing components, where these alloys serve as structural materials. Although the dynamic behaviour of additively manufactured materials is an expanding area of study, the high strain rate properties of CuCrZr remain not exhaustive and require further investigation. This study presents the results of quasi-static and dynamic tension-compression tests conducted at various strain rates on CuCrZr alloy specimens in their as-built condition. The alloy was fabricated using laser powder bed fusion (L-PBF) with selective laser melting (SLM) technology. Compression samples were designed with standard cylindrical shapes, whereas tensile sample geometry was tailored to meet dynamic testing requirements. The study involves the calibration of an improved Johnson-Cook constitutive model through inverse analytical and numerical procedures. Dynamic increase factors (DIFs) were also evaluated using phenomenological and physical model parameters. The findings indicate that CuCrZr alloy exhibits strain rate sensitivity, which activates above a certain threshold. This was confirmed by a reconstructed dynamic fracture locus, which was consistently higher than the quasi-static locus across all stress triaxiality values.

In the present paper, the effectiveness of the use of Machine Learning techniques, in particular Deep Learning algorithms, in the analysis of Ti-6Al-4V (Ti64) manufacture is studied; relationships between the values of physical parameters used during the production and mechanical characteristics are defined by means of the analysis of images taken from sections of the specimens, where defects and microstructural discontinuities can be observed. The Deep Learning approach, widely used for image classification and features extraction, also in this case shows promising possibilities, as proved by the implementation results reported.

The present study of Ti6Al4V alloy production via Electron Beam Melting (EBM) represents a cutting-edge research topic impacting different strategic engineering applications. This can be attributed to the widespread use of this alloy and by the unique characteristics of the EBM process. Operating under vacuum and with powder pre-heating, EBM enables the fabrication of components with higher density and reduced residual stress compared to other additive manufacturing techniques. The research reported in this paper analyses the effect of process parameters used in the manufacturing process on defect formation and then on mechanical properties. The results highlighted that the presence of lack of fusion defects leads to a markedly anisotropic behavior of the alloy. This is due to the different morphology of the defects in the different considered directions and to their effect in concentrating stresses.

Novel high entropy alloys (HEAs) have been greatly studied due to their structural and mechanical properties. Considering that some of the alloying elements used for producing these alloys are the same used for hydrogen electrocatalysis, few recent studies have been performed for evaluating the effectiveness of these alloys in the hydrogen catalysis. In this research novel FeMnCuNiTi and FeMnCuNiMo alloys were studied. These chromium and cobalt free HEAs were produced by using a centrifugal induction furnace and characterized to highlight their microstructure in the as-cast condition and after homogenization thermal treatment carried out at 1000 degrees C. The tested alloys, before and after thermal treatment, were also subjected to electrochemical characterization by performing cyclic voltammetry tests to determine the conditions for attaining the best electrocatalytic performances. The results showed that the tested alloys have considerable electrocatalytic activity, comparable with that of commercial alloys containing platinum. These properties could be improved after thermal treatment.

Engineering reliable metallic components across transportation, energy, manufacturing, and cryogenic technologies hinges on controlling how processing routes determine microstructure and how microstructure governs strength, toughness, and durability [...]

Laser Powder Bed Fusion is the most attractive additive manufacturing technology for its capability to produce metal components with complex geometry. One of the main drawbacks is the poor surface roughness. In this work, different scan strategies and process parameters were studied and their effect on surface roughness, alloy microstructure, and metallurgical defects were discussed. The results highlighted that only tailored process conditions could combine acceptable roughness and absence of metallurgical defects. For the upskin, it has been seen that, although by increasing the Volumetric Energy Density value the Ra decreases, Volumetric Energy Density values higher than 69 J/mm3 determine meltpool instability with consequent formation of gas defects in the subsurface area. Similarly, by increasing the Linear Energy Density value, the Ra of the lateral surfaces decreases, but above 0.37 J/mm, metallurgical defects form in the subsurface area. This study also highlighted that the proposed process involves only a contained increase of the production times. In fact, the evaluation of the increased production times, related to the adoption of this multi-scanning strategy, is of fundamental importance to consider if the proposed process can be advantageously applied on an industrial scale.

The increasing demand for designing complex structures using Functionally Graded Material boosts the research on reliable joining processes. For several industrial applications in the automotive, tooling, and petrochemical industries, the joining of a stainless steel with a low-alloy steel is often required to obtain a variation of mechanical and corrosion properties when different parts of the same structure are subjected to different working conditions. Welding a stainless steel with a low-alloy steel is a challenging operation because it is not easy to control the microstructure of the welded joint and to avoid metallurgical defects such as hot cracks. Moreover, traditional welding methods can only be applied to relatively simple geometries. To design and produce multi-material components, characterised by complex geometries, Selective Laser Melting process capabilities can be exploited. In this paper, an AISI 316L stainless steel is joined to 16MnCr5 steel by carefully tuning the process parameters. Metallurgical investigations coupled with Energy Dispersion Spectroscopy analyses allowed to evaluate the soundness of the joint and the effect of the process thermal cycle on the alloy microstructures and properties. The results are very promising and show that a careful selection of process parameters allows to obtain a continuous joint.

Amongst Additive Manufacturing (AM) processes, Powder Bed Fusion (PBF) technologies represent one of the most promising production methods for polymers and metals, and the laser-based systems are certainly the technology that currently guarantee the production of metal parts with complex geometries, shapes, and mechanical properties comparable to those of parts produced using traditional methods. A functionally graded material (FGM) or a multi-material (MM) component can be advantageously produced with several processes and laser-powder bed fusion (L-PBF) is one of the metal-based process for their production and design. In this scenario, the paper proposes a procedure to manufacture FGM or MM parts with standard L-PBF machines, that is equipped with only one powder deposition system, using the 2D multi-material approach, where the material transition occurs between the layers with a material change along the building direction. Joints between materials of common interest, such as AISI 316L CuCrZr alloy, AISI 316L 16MnCr5 steel, and Al-Sc AlSi10Mg alloy, were considered. The joints were analysed by means of metallographic investigation, neutron tomography (NT) analysis and tensile tests. The results of metallographic and tomography analyses highlight the continuity of joints establishing the possibility and the effectiveness to manufacture FGM or MM. Also, the tensile tests showed interesting results, demonstrating that the mechanical properties of the joint depend on the bulk alloy properties and on the internal structural integrity.

γ-TiAl-based alloys have been studied for many years because they are interesting candidates for the production of mechanical components working at high temperature. Increasing toughness and mechanical resistance of these alloys is crucial for boosting their application. In this paper, after having selected its composition, the alloy was produced by centrifugal casting and was reinforced by using Al2O3 nano-and micro-dispersoids. Four-point bending tests performed at high temperatures highlighted that the addition of 2% of Al2O3 is more effective than 3% of Al2O3 in increasing the alloy mechanical properties over the 800-900°C temperature range. The study revealed that this can be explained considering that a lower percentage of dispersoids allows to improve the oxide dispersion and to decrease the dispersed particle size.

Laser powder bed fusion is one of the most common metal additive applications for manufacturing industry and high-level research. It is common to have in a company, mechanical workshop or laboratory, machines of different manufacturers and powders of different suppliers. Therefore, there is the need for users of this technology to transfer optimized process parameters easily and quickly from one machine to another. Despite several multiphysics models being available, they are not always easy to use, especially by technical staff. Furthermore, particularly attention must be given to machines equipped with small laser spot size (i.e., < 50 µm) that are able to produce complex geometry with a fine resolution and smooth finish. Generally, these machines produce a deeper melt pool and are employed with fine powder (e.g., 5–35 µm) and consequently small layer (e.g., 20–40 µm). In this paper, simple and analytical rules to adjust the main process parameters (i.e., layer thickness, hatch distance, etc.) and to scale the volumetric energy density on a machine with a fine laser spot size have been proposed. Relative density, microstructure, and mechanical performance have been evaluated for AISI 316L stainless steel and 16MnCr5 case hardening steel. The results show that after a careful tuning of process parameters, it is possible to obtain relative densities close to 100

CuCrZr alloy plays a fundamental role for the production of critical components because it is characterized by good thermal and electrical conductivity and by high mechanical strength after precipitation hardening treatment. In the framework of a wider research on the mechanical behaviour of additively manufactured CuCrZr alloy, this study focuses on the effects of heat treatment parameters on the alloy strength. The additive manufacturing process, characterized by very high cooling rates, determines the formation, in the as-built condition, of a supersaturated solid solution. The results obtained reveal that aging temperature and time are critical parameters for improving the mechanical behaviour of CuCrZr alloy which behaves differently than the alloy produced through the use of traditional techniques.

A Ti-45Al-3Cr-2.5Nb alloy reinforced with in situ formed alumina has been produced by means of centrifugal casting by adding zirconium oxide in the crucible. The dispersion-strengthened alloy has been characterized to verify its microstructure and particle distribution. Mechanical tests carried out over the temperature range 850–950 °C highlighted that in situ formed alumina allows to increase the alloy yield stress by 21% at 850 °C and by 35% at 900 °C. Moreover, the in situ formed oxide particles produced an increase of the Young’s modulus of about 10% at 850 °C and of about 8% at 900 °C. Considering that the tested alloy has a density that is about a half of nickel superalloys, obtaining high specific mechanical properties over the temperature range 850–950 °C can boost its application in the production of turbine blades. Graphical abstract

The structural integrity of mechanical components is assessed by FBG sensors in many industrial fields. The FBG sensor has a relevant application at very high or low temperatures. To avoid the variability of the reflected spectrum and the mechanical properties degradation of the FBG sensor, metal coatings have been used to guarantee the grating's integrity in extreme temperature environments. Particularly, at high temperatures, Ni could be a suitable selection as a coating to improve the features of FBG sensors. Furthermore, it was demonstrated that Ni coating and high-temperature treatments can recover a broken, seemingly unusable sensor. In this work, two main objectives were pursued: first, the determination of the best operative parameters to achieve the most compact, adherent, and homogeneous coating; second, the correlation between the obtained morphology and structure and the FBG spectrum modification, once Ni was deposited on the FBG sensor. The Ni coating was deposited from aqueous solutions. By performing heat treatments of the Ni-coated FBG sensor, it was investigated how the wavelength (WL) varied as a function of temperature and how that variation was caused by the structural or dimensional change of the Ni coating.

Starting from the research aimed at the development of substitute alloys for stainless steels, with the aim of replacing strategic metals such as chromium and nickel with the more available manganese, FeMnAlC alloys have been studied and developed for several years. These alloys exhibit an attractive strength/ductility combination, low density, and some of them show good oxidation behaviour at high temperatures. After a preliminary study, in this paper the effect of a solubilization treatment followed by aging in the temperature range 550 - 750 °C has been evaluated. The results of the investigation revealed that the steel characterized by the higher amount of Mn and Al shows, after heat treatment, the formation of phases that make the alloy very brittle. Considering the obtained results, it is evident that optimizing the alloy chemical composition is of paramount importance to guarantee a high fracture toughness if the steel works for limited time intervals at high temperature.

The recycling of lead acid batteries (LABs) comprises relevant concerns on the suitable methodologies to recover lead. In this investigation, two electrorefining processes, by using acidic and alkaline electrolytes, have been compared to determine the most significant results of both methodologies. Acidic electrolytes used 200 g/L HBF 4 , 1.2 g/L H 3 PO 4 , 10 g/L H 3 BO 3 , and 100 g/L PbO, while the alkaline ones employed 120 g/L NaOH, 75 g/L PbO, 50–92 g/L glycerol, and 2 g/L gelatin. All the solutions were studied by varying temperature and current density (CD) to determine remarkable changes on current efficiency (CE), cell voltage (CV), specific energy consumption (SEC), and on the deposit quality. The results highlighted that by using the acidic electrolyte containing dextrin it is possible to obtain a compact deposit even using high CDs. Acidic solution without dextrin addition allows to obtain good quality deposits by working at 40 °C and 100 A/m 2 CD. After testing the behavior of different alkaline electrolytes, it is possible to observe that the solution containing the highest glycerol concentration allows to obtain, for intermediate valued of CD, CE higher than 97% with a SEC of about 0.37 kWh/kg. By comparing the results it is evident that the acidic electrolyte is the one that allows to reach higher productivity with lower SEC. In the selected conditions, lead deposits appear pure and compact. Graphical Abstract