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The requirement to join two dissimilar aluminium alloys produced with two different technological processes, extrusion and die casting, is fundamental in the automotive sector. In this research study was proposed the use of the Friction Stir Welding process to replace the traditional welding process. First of all was verified the weldability by using different process parameters and the results are reported in terms of microstructure and join aspect, which influence the Vickers microhardness. They show a suitable combination between the selected process parameters and the tool choice but also suggest to test different process conditions. Tool geometry and workpiece setup have to be redesigned. The final aim of this preliminary study is to find the best process conditions in order to proceed with components and machine tools design in the perspective of procedure industrialisation for hybrid vehicles battery pack assembly.

In the context of Industry 4.0, the interest towards the additive manufacturing processes is growing due to their numerous advantages, such as the possibility to prototype, the reduction of waste material, the inferior time to market, ad so on. In particular, a promising technology is the Direct Laser Deposition, which uses a focused laser beam to melt powders as there are deposited. In opposition to the well-established powder-bed fusion technologies, there are still some issues related to this process. This work aims to solve one of them, exploring the potentialities of DLD in printing thin-wall structures. For this purpose, the influence of the adopted deposition strategy and of the layer thickness on the geometrical accuracy and mechanical properties has been investigated. The results have pointed out that the first variable strongly influences the workpiece. It is possible to deposit thin-wall structures with a ZigZag strategy and consider a layer thickness equal to 90% of the height of the single track, printed with the same process parameters.

This experimental study investigates the effects of process parameters for 3D printing polylactic acid (PLA) samples on both the mechanical properties obtained and the energy consumption in the fused deposition modelling (FDM) process. The explained experimental activities provide an in-depth evaluation of all the strategies adopted in different temperatures and scan speed strategies. The results, extracted in tensile strength, ultrasonic inspection (UT), and specific energy consumption (SEC), highlight the printing parameters that mainly affect the mechanical characteristics of the final workpieces and the energy consumption to find an appropriate energy-saving energy strategy for the PLA additive manufacturing process. The results indicate a more excellent uniformity of the molded material, reducing the printing time and total energy consumption at high speeds (V = 110 mm/s) and one level of temperature (T = 215 °C). A new efficiency index has been introduced to release guidelines to pursue the best setup compromise.

Additive manufacturing is an advanced technology able to produce parts with different grades of complexity, including its shape, microstructure, functionality and material. Regarding material complexity nowadays, it is possible to produce polymer parts with customized reinforced fibre filling such as carbon, Kevlar or glass. These new techno polymers could guarantee good mechanical properties with low cost production, and so different industrial sectors started to implement them in parts design. However, their mechanical behaviour is still under investigation, and many about their mechanical behaviour are still unknown. In this article the authors present the experimental characterization of polymer filled with Kevlar to pin bearing test. Samples have been designed as a function of filling and geometry parameters. Results have been analyzed with statistical methods. Finding highlight similar and different behaviour regarding samples produced with conventional process.

The increasing production of hybrid electric vehicles draws the attention to the importance of lightweight structures and energy storage improvement. These objectives are pursued by using dissimilar aluminum alloys and customized parts, provided by different manufacturing processes, including additive manufacturing. This leads to the need of improving the joining procedure in challenging situations. The replacement of the traditional welding process, with a setup suitable for FSW, is investigated by this research study. An industrial component to be assembled was chosen, an extruded AA6063-T6 workpiece, which was welded to an AlSi10Mg 3D printed item. Different welding conditions were considered and investigated through metallography inspections and mechanical tests of the joints. All the tested welding showed a good quality proved by the stability of the tensile tests and the consistency of the microhardness measurements. The SEM analysis showed an optimal mixing. The promising results reported encourage for continuing in an industrialization perspective.

This research activity deals with 3D printing composites fabricated by Continuous Fiber/Filament Fabrication with an innovative thermoplastic matrix infilled with microcarbon fiber, i.e., Onyx, and carbon reinforcement. Three groups of additively manufactured samples were printed and tested to evaluate the possibility of avoiding the drilling phase to increase the bearing resistance and evaluate the parts’ properties: standard geometry, post-process drilling, and customized geometry. Different configurations were realized for the additively manufactured and drilled samples to assess the reinforcement effect on the bearing performance and identify the 3D printing technology limits. Finally, the customized sample represents a new approach to conceiving a better solution for enhancing the bearing strength. Pin-bearing stress and stiffness have been analyzed through experimental methods, the material compaction quality was detected by ultrasound technique, and failure modes have been discussed. Concerning the additive samples, the bearing strength decreased in all reinforced printed configurations due to the technological limitations of the CFF process. However, exploiting a more flexible approach in the design, a novel bearing configuration with a custom infill strategy was proposed, reaching high values of bearing strength and stiffness. This resulted in a reduction in costs and weight, taking one step toward more sustainable production.

Additive manufacturing technologies of metals are gaining increasing interest due to several advantages; among these processes the selective laser melting (SLM) is of particular interest for industrial applications. Despite the clear advantages related to this technique, there are some issues that still hamper a mainstream industrial application of SLM, one is the repeatability of the process. It is well known that varying, for instance, the building direction or the position in the building chamber the components obtained show different microstructures and mechanical properties, several authors are trying to develop processing routes aiming to increase the repeatability of the process. Another issue is the fact that different SLM equipment, produced by different manufacturers, even if the process parameters adopted are the same will lead to the production of components with slightly different properties. These differences are due to small differences among the different equipment, for instance the gas used in the chamber or the way the laser is delivered. The scope of this work is to investigate the mechanical properties of AlSi10Mg components produced with different SLM machines: EOS M400, SLM 280 and RENISHAW AM400. Aiming to assess which are the differences and try to find a range of properties that can be assumed for SLMelted parts. Tensile specimens, designed according to ASTM standard, were printed with the above-mentioned equipment and tensile tests were carried out. The results obtained showed that slight differences can be outlined among the different samples and a range of tensile properties has been also proposed.

The cold spray deposition process has gained interest as a promising technique for producing metallic coatings on polymers and composite materials thank to its low working temperatures. However, poor adhesion of metallic particles on polymeric substrates and the brittle nature of these materials lead to generation of cracks under the impact of the sprayed particles, limiting its application to polymeric matrix composite. The interposition of an intermediate metallic layer over the thermoset composite to be coated has been claimed to improve the adhesion of the sprayed particles and the formation of a stable link between the metal coating and the underlying polymer panel. The present work discusses a methodology that integrates the manufacturing of glass reinforced epoxy panels having functionalized surface and the subsequent production of a dense metallic layer by cold spray. Pure copper and titanium metallic powders, having spherical and irregular shape respectively, were placed on the top of the stack of dry glass fiber fabrics. Resin infusion process was then applied to impregnate the glass fabrics providing the simultaneous functionalization of the composite panel. In order to assess the effectiveness of the produced substrate, and of the proposed procedure, metallic coatings have been finally deposited on manufactured composite panels by means of a low-pressure cold spray facility. Regardless the spraying condition (namely gas temperature, stand-off distance, sprayed particles), copper samples showed a remarkable erosion of functionalized layer after cold spray process with pronounced damages of the composite substrate. On the other hand, effective depositions have been observed on titanium samples under specific combination of process parameters.

In recent years, the aircraft industry has shifted its preference for metal parts to titanium and its alloys, such as the high-strength Titanium Grade5 alloy. Because of Titanium Grade 5 limited formability at ambient temperature, forming operations on this material require high temperatures. In these conditions, a peculiar microstructure evolves as a result of the heating and deformation cycles, which has a significant impact on formability and product quality. On the other hand, additive manufacturing technologies, as selective laser melting and electron beam melting, are increasingly being used and are replacing more traditional approaches such as machining and forging. Fundamental parts characteristics as mechanical and microstructural properties, geometric accuracy and surface quality strongly depend on the selection of the manufacturing method. The authors of this paper seek to identify the strengths and limitations imposed by the intrinsic characteristics of different manufacturing alternatives for the production of parts of aeronautical significance, providing guidelines for the choice of the most appropriate manufacturing route for given application and part design.

Ti-6Al-4V alloy is characterised by having excellent mechanical properties and corrosion resistance combined with low specific weight and biocompatibility. This material is ideal for many high-performance engineering applications. It is increasingly used in additive manufacturing (AM) thanks to the possibility of producing very complex lightweight structures, often not achievable with conventional manufacturing techniques, as well as to easily customise products according to specific customer requirements. In powder bed fusion (PBF) processes, only a small percentage of the powder is actually melted and solidified to achieve the final part while most is left after the build. Since the surface morphology and chemistry, the shape and size distribution of the un-melted particles are inevitably modified during the process, and this may affect the resulting properties of the final products, many companies tend to use virgin powders for AM builds to keep compliance with manufacturing requirements and minimise risk. From both an economic and environmental point of view, it results crucial to develop recycling methods to reuse the metal powder as many times as possible while maintaining compliance with manufacturing standards. In this work, the effect of Ti-6Al-4V powder reuse on the evolution of powder characteristics and mechanical properties of final products additively manufactured is investigated through a systematic approach based on design of experiments.

Among the several additive manufacturing techniques, Fused Filament Fabrication (FFF) is a 3d printing technique fast, handly and low-cost to produce complex-shaped parts easily and quickly. FFF adds material layer by layer, saving energy, costs, raw material costs and waste. Nevertheless, Among the recent papers, analysis is absent on the impact performance of 3D printed composites. The response to low-velocity impact events is a crucial issue for composite materials, for the operational reliability of the element that has experienced a great reduction of mechanical strength due to their anisotropic nature. However, there is a lack of knowledge, mainly about the impact behaviour of 3d printing composite materials, also considering that the main demand comes from the transportation field (automotive, aircraft, etc.), where the impact event is always possible. Thus, the aim of this research is to begin to fill the knowledge gap investigating the impact behaviour of specimens obtained by continuous fiber fabrication technique. Onyx and Nylon white filaments were used as matrices and glass fibres for reinforcement. The present paper deals with the manufacturing of composite material items obtained by the Markforged FFF technique. An innovative matrix of nylon and micro carbon fibre (ONYX) was used with and without glass filament as reinforcement. Low velocity impact tests at penetration were carried out to study the impact performance of the novel material and the effect of the reinforcement used.

Microneedle (MN) patches are highly efficient and versatile tools for transdermal drug administration, in particular for pain-free, self-medication and rapid local applications. Diffraction ultraviolet (UV) light lithography offers an advanced method in fabricating poly(ethylene glycol)-based MNs with different shapes, by changing both the UV-light exposure time and photomask design. The exposure time interval is limited at obtaining conical structures with aspect ratio < 1:3, otherwise MNs exhibit reduced fracture load and poor indentation ability, not suitable for practical application. Therefore, this work is focused on a systematic analysis of the MN's base shapes effects on the structural characteristics, skin penetration and drug delivery. Analyzing four different base shapes (circle, triangle, square and star), it has been found that the number of vertices in the polygon base heavily affects these properties. The star-like MNs reveal the most efficient skin penetration ability (equal to 40 % of -their length), due to the edges action on the skin during the perforation. Furthermore, the quantification of the drug delivered by the MNs through ex-vivo porcine skin shows that the amounts of small molecules released over 24 h by star-like MNs coated by local anesthetic (Lidocaine) and an anti-inflammatory (Diclofenac epolamine) drugs are 1.5× and 2× higher than the circular-MNs, respectively.

Nimonic 75 sheets were cold-spun under different processing conditions and then heat-treated. The microstructure evolutions occurring during the process were studied and discussed in details. The results obtained showed the feasibility of the process when adopting low values of the tool feed rate. Metal spinning produces a deformed microstructure, different in the several areas of interest of the final component. The chosen heat treatment promoted the annealing of the material across the whole part.

Metal Additive Manufacturing technologies development is increasing in a remarkable way due to their great potential concerning the production of complex parts with tailored characteristics in terms of design, material properties, usage and applications. Among all, the most widespread technologies are the Powder Bed Fusion based technologies such as Selective Laser Melting and Electron Beam Melting. However, the high surface roughness of the as-built parts still represents one of the major limitations, making necessary the adoption of post-process finishing to match the technological requirements for most of the fields of application. In this scenario, Fluidised Bed Machining represents an emerging finishing technology that could overcome some of the limitations of the most common methods, especially in terms of feasibility for the treatment of complex parts thanks to the fluid-like mobility of the abrasive material. This work deals with the preliminary tests of the Fluidised Bed Machining of additive manufactured samples using alumina as the abrasive material, investigating the effects of a high abrasive/substrate hardness ratio condition. The experiments were carried out on small plates of AlSi10Mg alloy made through Selective Laser Melting technology, built in the vertical direction with respect to the building plate. The influence of the impact angle and treatment time were investigated under bubbling fluidization conditions. Surface morphology evaluations were carried out pre and post process by means of Confocal Microscopy and Scanning Electron Microscopy (SEM). Weight loss measurements were conducted to evaluate the material removal rates as well. Results show a small influence of the specific impact angle, a slight reduction of the surface roughness and an asymmetrical effect of treatment, acting mostly on the sintered powders forming the peaks of the as-built surface.

Fused deposition modeling (FDM) is an additive manufacturing technology where three-dimensional physical models are manufactured by layer-by-layer deposition. However, the layered surface built with FDM suffers from poor surface quality and dimensional accuracy even for basic part geometries. This proves to be unacceptable and not satisfactory for most general purposes with the consequence of a decreased value of the final product. Several methods for post-processing were proposed to achieve fine surface of manufactured components. In particular, for components manufactured with polylactic acid (PLA) the chemical post-processing with dimethyl ketone (acetone), named vapor smoothing process, seems to be very promising to significantly improve the surface roughness. Moreover, acetone has the main advantage to have a low cost, low toxicity and high diffusion rate. However, this polishing procedure may dissolve the outer surface of the parts affecting the structural reliability of the part. In this work, a novel device, consisting of a cylindrical chamber in Pyrex, is set-up for the vapor smoothing process with acetone. The system is designed to permit the injection of a gas containing acetone at different concentrations and at different operating conditions (temperature, contact time). The samples used for the test are truncheon design manufactured using different printer settings; each truncheon is built at inclination angles varying from 0° to 45° in step of 5°. The variation of the surface roughness was investigated using a confocal microscope Leica DCM3D, equipped with the software LeicaScan and LeicaMap.

Additive manufacturing refers to a wide class of manufacturing processes based on the progressive building of functional parts through the addition of material layer upon layer. These technologies were first confined to prototyping, but the subsequent development of additive manufacturing processes for further materials, such as metals, has encouraged their worldwide industrial spread, from the biomedical field to the automotive and the aerospace industries. Additively manufactured parts are required to meet high and stable performance, at least comparable to that of conventional wrought materials, so as to comply with strict and well-defined international standards. This paper presents an investigation into the mechanical properties of AlSi10Mg parts produced by laser powder bed fusion technique, using different spatial orientations within the build volume. The effects of the part position and orientation on the static (tensile) properties of the produced parts were assessed by means of the two-way analysis of variance technique. The build angle was found to be the most effective parameter, while the variability ascribable to the effect of part position resulted mainly as physiological. The fatigue resistance showed a globally decreasing trend with increasing build angle.

In the context of Industry 4.0, interest is increasing towards Additive Manufacturing processes due to their several advantages. Among these, the Direct Laser Deposition (DLD) is an innovative technology for additive metal part fabrication, and it is currently demonstrating its ability to revolutionize the manufacturing industry. It is particularly interesting for industrial applications in terms of reduction of waste materials by starting with fewer feedstocks, reduction of machining time by only have material where it is needed but, above all, it is interesting to extend the life of parts. Indeed, with the DLD, it is possible to repair an item or coat parts via cladding, making it more wear-resistant. It is also possible to give "another life" to broken or waste components, for example, by replacing the damaged area using new material. Moreover, particularly intriguing is the possibility to create hybrid or graded parts by varying material/alloy concentrations. This paper aims to combine the abovementioned advantages to develop tailored structures in order to accomplish complex and functional products. For this purpose, a specific case study was investigated, starting with the study of the appropriate powders to use and ending with the printing process using the DMG Mori Lasertec65. Microstructural and mechanical analyses were carried out to evaluate the products and to validate the process. The final results show the properties and performances of products obtained using this technology.

An innovative additive manufacturing technique is reported, which enables 3D printing of lightweight cellular structures with multiscale density control and carbon fibre reinforcement to improve mechanical performances. We present a model-based design of the process (including heat transport in the 3D printer nozzle) allowing to control the foam morphology in the printing process. The proposed approach is validated using polylactic acid, which is a bio-based compostable polymer employed in the biomedical, agricultural, and chemical engineering fields, that is blown with carbon dioxide to produce both reinforced foamed strands and structures. These have been characterized by microscopy and mechanical tests. The results show that the addition of fibres in the polymer matrix induces cells breakage resulting in a double-cell-sized morphology. The mechanical characterization of our 3D printed lightweight cellular composites revealed that the reinforced cellular structures have a higher compression strength than the non-reinforced ones.

The customization of material characteristics in combination with extreme design flexibility represents the most intriguing scope of Additive Manufacturing. In this context, this work investigated the feasibility of the Laser-based Powder Bed Fusion process (L-PBF) of pre-mixed Inconel 718-Cu powder blends, exploring the effects of the laser-related process parameters and Cu addition, in order to develop alloys able to combine excellent mechanical properties under severe operating conditions with good thermal and electrical conductivity. More specifically, this work investigated the effects of using a layer thickness of $\boldsymbol{30 \mu \mathrm{m}}$ on the process quality in terms of density, microhardness, microstructure and surface roughness. Results showed that cubic samples with 10 mm side were successfully produced, with a relative density always greater than 98 percent. The resulting microhardness was from 290 to 340 HV, decreasing as a function of the Cu addition and keyhole defects development. The latter were the main defects observed in the microstructure, characterized also by heterogeneous crystalline grains for all the investigated conditions. Finally, the surface roughness (Sa) was from 7 to $\boldsymbol{25 \mu \mathrm{m}}$ , in line with the typical values of L-PBF products.

Among the several additive manufacturing techniques, fused filament fabrication (FFF) is a 3D printing technique that is fast, handy, and low cost, used to produce complex-shaped parts easily and quickly. FFF adds material layer by layer, saving energy, costs, raw material costs, and waste. Nevertheless, the mechanical properties of the thermoplastic materials involved are low compared to traditional engineering materials. This paper deals with the manufacturing of composite material laminates obtained by the Markforged continuous filament fabrication (CFF) technique, using an innovative matrix infilled by carbon nanofibre (Onyx), a high-strength thermoplastic material with an excellent surface finish and high resistance to chemical agents. Three macro-categories of samples were manufactured using Onyx and continuous carbon fibre to evaluate the effect of the fibre on mechanical features of the novel composites and their influence on surface finishes. SEM (Scanning Electron Microscopy) analysis and acquisition of roughness profile by a confocal lens were conducted. Tensile and compression tests, thermogravimetric analysis and calorimetric analysis using a DSC (differential scanning calorimeter) were carried out on all specimen types to evaluate the influence of the process parameters and layup configurations on the quality and mechanical behaviour of the 3D-printed samples.

Poor surface quality represents one of the most critical drawbacks of metal parts produced by powder bed-based Additive Manufacturing (AM) technologies, such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM). Among the several post-process surface finishing treatments, Fluidised Bed Machining (FBM) could represent an intriguing and cost effective option for the treatment of complex AM metal parts. This work illustrates the results of the preliminary tests carried out by means of the FBM technology in which an external contribution of rotational speed of the samples was introduced. Rotation of the samples was considered in order to increase the relative speed and energy dissipation between the parts and the fluidised abrasive particles, with the aim to increase the process efficiency in terms of surface roughness reduction. For the experiments, AlSi10Mg alloy square flat samples were built in vertical direction by means of SLM technology and dipped into an abrasive fluidized bed of silica sand. The preliminary tests were carried out by adopting a minimum fluidization regime of the abrasives and establishing, through the rotation of the samples, two values of mean superficial tangential speed of 1 m/s and 2 m/s. The effect of the latter was investigated in combination with different impact angles, considering a process time of 30 min. The surfaces were characterized quantitatively by means of confocal microscopy and weight loss measurements, while SEM images were acquired in order to observe the real morphology evolution after the treatment. The experimental results suggested a slight surface modification and roughness reduction for the investigated FBM process conditions, due to a low energy transfer from the abrasives to the surfaces. On the other hand, the results shown also that a greater surface smoothing effect was achieved when increasing the tangential speed and adopting low impact angles.

Friction Stir Welding (FSW) is one of the most used solid-state welding processes in the aeronautical, aerospace, ground transportation and naval fields. Stationary Shoulder Friction Stir Welding (SSFSW) is a recently introduced variant of the process allowing lower heat input into the joints, with beneficial effects in terms of joint mechanical properties, microstructure and top surface finish. In the paper, lap joints produced by SSFSW and made out of AA6082-T6 aluminum alloy sheets have been analyzed with the aim to investigate the effect of the stationary shoulder on the lap joints surface, metallurgical, and mechanical properties. The lap joints produced by SSFSW have been compared to the ones produced by “conventional” FSW in order to highlight the differences between the two processes. The top surface of the joints obtained with the two processes has been quantitatively evaluated. Finally, a dedicated numerical model has been utilized to highlight the causes of the observed differences through the distributions of the main field variables, namely temperature, strain and strain rate. It was found that SSFSW results in narrower weld nugget and smaller areas involved by micro hardness reduction caused by smaller peak temperature and high temperature zone. Additionally, better surface quality was found for the joint welded by SSFSW with lower heights and flash, allowing to avoid subsequent finishing operations needed for most industrial applications.

The widespread additive manufacturing technology for producing components having complex geometries has increased the attention towards new reinforced materials, whose internal structure can be designed ad hoc on the required mechanical performance. Moreover, fused deposition modelling (FDM) technology allows the building of continuous fibre-reinforced thermoplastic composites. Due to this innovative technology, there is a lack of knowledge mainly about the impact behaviour of these materials, also considering that the main demand comes from the transportation field (automotive, aircraft, etc.), where the impact event is always possible. Thus, the aim of this research is the investigation of the impact behaviour of specimens obtained by continuous fiber fabrication technique, where Onyx and nylon white filaments were used as matrices and glass fibres for reinforcement. Onyx is a nylon mixed with short carbon fibres. An extensive non-destructive evaluation was performed on the specimens subjected to impact tests to assess the impact damage tolerance of these materials and to measure the damage extension as well. Nevertheless, considering that different non-destructive techniques were employed, the research aims also to suggest the most suitable and reliable technique to detect damage, mainly by on-site inspection.

The linear friction welding (LFW) of Ti-6Al-4V parts manufactured through electron beam melting (EBM) is investigated using different processing conditions of frequency (from 40 to 50 Hz) and press...

A preliminary research work is carried out to demonstrate the feasibility of friction stir welding of AlSi10Mg plates produced by selective laser melting. The metallurgical evolutions occurring have been studied and discussed on the basis of detailed microstructure observations. The FSW process enhances the structure of the parent material so that the weld presents an overall refinement of the microstructure and a decrease in microporosity in all its zones. Using the friction stir welding technology, sound welds harder than the parent material can be obtained.

This paper aims to study the genesis of defects in titanium components made through two different additive manufacturing technologies: selective laser melting and electron beam melting. In particular, we focussed on the influence of the powders used on the formation of porosities and cavities in the manufactured components. A detailed experimental campaign was carried out to characterize the components made through the two additive manufacturing techniques aforementioned and the powders used in the process. It was found that some defects of the final components can be attributed to internal porosities of the powders used in the manufacturing process. These internal porosities are a consequence of the gas atomization process used for the production of the powders themselves. Therefore, the importance of using tailored powders, free from porosities, in order to manufacture components with high mechanical properties is highlighted.

Ba0.75Sr0.25 Al2Si2O8 (BSAS) ceramic was synthetized starting from a (Ba, Sr)-exchanged zeolite A. The substitution of Ba with Sr promoted the transformation of hexacelsian to monocelsian, which was attained by a 5 h thermal treatment at 1200 °C. BSAS systems were structurally and dielectrically characterized. In particular, the evaluation of dielectric properties was performed by impedance spectroscopy in a.c. The study of the dielectric and the spectroscopic characteristic was investigated in the frequency range (100 Hz - 1 MHz). The dependence of the dielectric constant on the frequency has been explained on the basis of the mechanism Maxwell-Wagner, comparing BSAS systems with commonly used ceramic materialsin radome manufacturing, such as fused silica (SiO2) and silicon nitride (Si3N4).Electrochemical Impedance Spettroscopy (EIS) also provides useful information about the microstructure of the ceramic materials. The curve of permittivity vs frequency showedthat the BSAS has a constant performance in the frequency range investigated with lower value of permittivity compared to the other materials investigated.

Titanium alloys are increasingly used for structural applications in transportation engineering (aerospace, automotive, railway, marine industry) because of their interesting properties (high mechanical properties to weight ratios, excellent corrosion resistance). In the present research work, the very high cycle fatigue behaviour of Ti–6Al–4V alloy of both bimodal and basketweave microstructures were investigated and compared. Fatigue tests at a very high number of cycles with R = −1 were carried out on titanium alloy - grade 5 specimens, cut from a forged flange used on a commercial aircraft. The experimental tests showed that this alloy has an always decreasing S-N curve, even for a number of cycles greater than 10 9 . It is the typical behavior of some alloys used in the aircraft industry, such as aluminum, titanium, nickel and high-strength steels. Moreover the very high cycle fatigue tests demonstrated that the Ti–6Al–4V alloy with bimodal microstructure has fatigue strength higher than the Ti–6Al–4V alloy with basketweave microstructure. The effect of microstructure on fatigue mechanism focused on internal crack initiation has been discussed through SEM observation of sub-cracks underneath the fracture surface. The temperature evolution during the tests was detected by means of IR cameras to study the temperature effect on the material response.

This paper is about the optimal selection of process parameters for Wire Arc Additive Manufacturing technology, an emerging solution for additive production of metal parts. In particular, the selection of the process parameters is based on the evolution of the microstructure and on the mechanical properties of the final samples obtained through the successive deposition weld beads of a ER70S-6 steel, according to the AWS legislation. The feed rate and the heat input during the deposition of the weld beads have been varied, in order to understand how the temperature reached by the samples can affect the final product mechanical characteristics. The final cooling has been carried in calm air at room temperature and between the deposition of a weld bead and the following one it has been imposed a pause of 60s. The tests on mechanical properties carried out have been: A full experimental campaign that includes: macrographic observations, micrographic observations and Vickers microhardness. The analysis of these tests has highligthed that by varying the process parameters, the samples do not have substantial differences between them. Instead, a microstructure that evolves from pearlitic-ferritic grains until bainitic lamellae along the vertical direction of the samples has been observed by micrographic analysis and confirmed by microhardness measurements.

Additive Manufacturing (AM), applied to metal industry, is a family of processes that allow complex shape components to be realized from raw materials in the form of powders. The compaction of the powders is achieved by local melting of bed. Electron Beam Melting (EBM) is an additive manufacturing process in which a focalized electron beam is the heat source that allows the powders to be compacted. By EBM it is possible to realize complex shape components; this feature is of particular interest in titanium industry where numerous efforts are done to develop near net shape processes. One of the limits of EBM based AM process is the difficulty to realize large dimension parts. Due to this limit the study of joining processes of different parts is of great interest. In the present work the microstructure evolution of sheets of TI6Al4V made by EBM and joined by Linear Friction Welding (LFW) is analyzed in details. The bulk microstructure of the specimen is fine lamellar; lamellae are enclosed in alpha colonies. Different types of porosities are observed. In the joint a Thermo Mechanical Affected Zone (TMAZ) and Weld Bead (WB) are evident. In TMAZ a partial recrystallization occurs and the parent microstructure is deformed. Complete recrystallization occurs in WB whose structure is martensitic.

TiO2 in the form of nanocrystals possesses photocatalyst properties leading to excellent capability of degrading a number of environmental contaminants such as organics, bacteria, and viruses. However, the antimicrobial activity of nano-TiO2 coatings against different microorganisms is not yet well established. Candida albicans, Aspergillus niger, Staphylococcus aureus and Streptococcus mutans are common nosocomial and environmental pathogens responsible for biofilm-associated infections especially in indoor environments. In this study, we produced thin coatings of TiO2 nanoparticles on aluminum substrates and assessed whether they may prevent fungi and bacteria biofilm formation and whether this may be a synergistic effect of TiO2 nanoparticles with UV irradiation, which is more representative of the natural conditions for passive devices. Coatings of flame-synthesized nanoparticles were produced by direct thermophoretic deposition on aluminum substrates through a rotating disk inserted in the flame. Particle and coating characterization was performed by means of differential mobility analysis, Raman and X-ray diffraction spectroscopy. Microbial biofilm formation on substrates with different TiO2 thicknesses were evaluated by the colorimetric crystal violet method and quantified by spectrophotometry in four different fungi and bacteria strains; the results were corroborated by scanning electron microscopy analysis. Substrates with minimal TiO2 nanoparticle layers demonstrated a strong anti-biofilm effect against both fungi and bacteria, due to the well-known cellular component photo-oxidation and to the enhanced nanomaterial surface area. Interestingly, UV irradiation of the substrates at a low intensity for a short time demonstrated a significant enhancement of the titania antimicrobial activity. TiO2 nanoparticle coatings may be proposed as self-cleaning and self-disinfecting materials able to reduce microbial infections, especially in indoor environments where hygiene is needed.

Linear friction welding (LFW) is an innovative solid-state welding technique that allows to manufacture joints with high mechanical properties. This technology has various applications in the aerospace field; in particular it is used to weld massive structural components made of Ti6Al4V. This paper deals with the experimental study of Ti6Al4V T-joints welded through LFW, with particular focus on the effectiveness of ultrasonic control in detecting and distinguishing welding defects within the joints. Aiming to this scope, joints with different properties were manufactured and tested: some were free from defects but with different metallurgy, and some had different types of defects. The results obtained proved that the ultrasonic control was an effective method to detect and identify defects in linear friction welded titanium joints, moreover it was possible to get information regarding the microstructure and in particular the extension of the different metallurgical zones induced by the welding process. © 2016, Shanghai University and Springer-Verlag Berlin Heidelberg.

In this paper, the feasibility and capability of friction stir processing to enhance material structure and surface properties of additively manufactured Ti6Al4V plates is investigated. The base material was produced by electron beam melting process and then friction stir processed using a pin less tool to compensate the provides poor surface finishing, reduced mechanical properties and internal porosity defects affecting the outer layer. A reduction by 80% of surface roughness was achieved. Internal porosity decreased as well. Microstructural analysis evidenced that the heating and stirring effects promoted the formation of distinct metallurgical zones, namely a stirred zone (SZ), a transition zone (TZ) and a heat affected zone (HAZ). The SZ exhibits a fully recrystallized microstructure, whereas highly deformed but not recrystallized grains and coarser grains were detected in the TZ and HAZ, respectively. Within the treated zone the hardness increased up to 450 HV with respect to 380 HV of the base material.

Additive Manufacturing (AM) can be considered today as a real production technology, which allows to realize parts with a complexity degree that, in some cases, is not achievable otherwise. However, one of the most relevant weak spots is the high surface roughness, especially for metal parts, making necessary the adoption of post-process finishing treatments. This paper deals with the preliminary investigations on the Fluidised Bed Machining (FBM) technology, in which a sample is dipped into a fluidized bed, i.e. a two-phase system where an abrasive, kept in motion through a gas, behaves like a fluid performing a huge number of impacts on the considered surface. This peculiarity could guarantee a high degree of homogeneity of the treated surface morphology. The influence of the impact angle has been investigated by conducting experiments with AlSi10Mg plates made by Selective Laser Melting Technology (SLM), and the fluidized bed operated in bubbling fluidization regime. The treatment has been carried out by dipping the samples for a total time of 3 hours and monitoring the results with a step of 30 min for the first 2 hours. The treated surfaces have been characterized by means of Confocal Microscopy and Scanning Electron Microscopy (SEM). Weight loss measurements have been carried out as well for a preliminary evaluation of wear. Results suggest a poor decrease in surface roughness (Sa), as also demonstrated by the poor weight loss, both due to a low impact energy of the abrasives. However, variations of other surface texture parameters (Sz, Ssk, Sku, Rdq), as well as SEM images, suggest that the main surface-abrasive flow interaction phenomena are micro-ploughing and micro-peening.Additive Manufacturing (AM) can be considered today as a real production technology, which allows to realize parts with a complexity degree that, in some cases, is not achievable otherwise. However, one of the most relevant weak spots is the high surface roughness, especially for metal parts, making necessary the adoption of post-process finishing treatments. This paper deals with the preliminary investigations on the Fluidised Bed Machining (FBM) technology, in which a sample is dipped into a fluidized bed, i.e. a two-phase system where an abrasive, kept in motion through a gas, behaves like a fluid performing a huge number of impacts on the considered surface. This peculiarity could guarantee a high degree of homogeneity of the treated surface morphology. The influence of the impact angle has been investigated by conducting experiments with AlSi10Mg plates made by Selective Laser Melting Technology (SLM), and the fluidized bed operated in bubbling fluidization regime. The treatment has been carried out ...

The effects of different heat treatments on Inconel 718 parts produced through selective laser melting were investigated. Different heat treatments, carried out by varying both temperature and time, were performed on 10x10x10 mm3 cubes. Aiming to study the effects of the treatments, microhardness measurements, optical and SEM observations were carried out on both the treated and the untreated samples. The results obtained proved the effectiveness of the treatment, if the conditions are properly set, in producing the typical microstructure of the cast Inconel 718 that is the starting point for the conventional heat treatments. A predominant influence of the temperature was also highlighted.The effects of different heat treatments on Inconel 718 parts produced through selective laser melting were investigated. Different heat treatments, carried out by varying both temperature and time, were performed on 10x10x10 mm3 cubes. Aiming to study the effects of the treatments, microhardness measurements, optical and SEM observations were carried out on both the treated and the untreated samples. The results obtained proved the effectiveness of the treatment, if the conditions are properly set, in producing the typical microstructure of the cast Inconel 718 that is the starting point for the conventional heat treatments. A predominant influence of the temperature was also highlighted.