bluuebunny/crossref_metadata_2025 huggingface dataset:
The relationship between preoperative inflammatory indexes and adherent perinephric fat in laparoscopic partial nephrectomy
Authors: Çil Gökhan , Yilmaz Mehmet , Yentur Serhat , Çolakerol Aykut , Canıtez İbrahim
Published: November 2024

Background/Aim: Partial nephrectomy (PN) is favoured for cT1a renal tumours. However, factors like adherent perinephric fat (APF), linked to prolonged operation time due to chronic inflammation are often overlooked. The objective of this study was to assess the relationship between the composite inflammatory index and APF in patients with renal cell carcinoma (RCC) prior to laparoscopic partial nephrectomy (LPN). Methods: The retrospective analysis included 189 LPN patients from April 2015 to June 2021, categorised by APF presence. Demographic, laboratory and radiological data assessed composite inflammatory index and Mayo adhesion probability (MAP) scores. Chi-Square and Mann-Whitney U-test analysed categorical and continuous variables. Area under curve (AUC) measured parameter discrimination. Logistic regression identified APF predictive factors. Results: APF was present in 90 patients (47.6 %). The APF-positive group had significantly higher C-reactive protein (CRP) levels and longer operation times (p = 0.016 and p = 0.001, respectively). Elevated MAP scores and systemic inflammatory index (SII) values were also observed in the APF-positive group (p = 0.002 and p = 0.001, respectively). Receiver operating characteristic (ROC) analysis determined SII's cut-off at 600 (sensitivity: 60.0 %, specificity: 60.6 %, AUC: 0.640, p = 0.001), MAP score at 2.5 (sensitivity: 67.8 %, specificity: 64.5 %, AUC: 0.640, p < 0.001) and operation time at 122.5 min (sensitivity: 74.4 %, specificity: 67.7 %, AUC: 0.807, p < 0.001). Conclusion: Presented results indicate that SII is linked to APF in patients undergoing LPN and may serve as an independent predictor of APF positivity.
A unique manifestation of postural orthostatic tachycardia syndrome (POTS) resembling symptoms of irritable bowel syndrome
Authors: Alshmandi Mohamed , Khan Jasim , Kiernan Julia
Published: November 2024

Postural orthostatic tachycardia syndrome (POTS) exhibits a broad spectrum of presentations, with severity varying from individual to individual. These diverse symptoms vary from person to person but usually presents with palpitations, dizziness, blurred vision, mental fatigue, collapse, shortness of breath and chest pain. It may also manifest with less usual presentations including abdominal symptoms that can often go misdiagnosed or undiagnosed for a long time. A case of a 29 years-old woman, who was hospitalised for evaluation of persistent abdominal discomfort accompanied by bloating and chronic episodes of watery diarrhoea is presented. Diagnosis of POTS was established. It's crucial to consider POTS in the differential diagnosis for patients displaying autonomic symptoms, including those related to the abdomen.
MXene: A new revolution in the world of 2-D materials
Authors: Garg Ruby , Agarwal Mohit
Published: November 2024

MXenes have imposed a profound effect on materials science and nanotechnology fields after their discovery in 2011. Theoretical models have predicted more than 100 potential compositions of MXene whereas laboratory-scale synthesis reflects their success of over 40 distinct structures till date. The distinctive properties of MXenes have led to their use for a diverse range of applications, such as energy storage, environmental remediation, electronics, communications, gas and liquid separation and adsorption, biomedical fields, and optoelectronics. The increased interest of researchers in MXenes has led to a wide rise in research publications, showing their growing importance in different scientific domains. In 2024, MXenes had shown wide potential in various areas, including energy storage devices, electromagnetic interference shielding, nanocomposites, and hybrid materials. However, the variations in the choice of precursors, reactor design, cost, synthesis parameters pose several challenges in ensuring the production of high-quality MXenes. The applicability of MXenes continues to broaden as its compositions are continuously accelerating. This review aims is to provide a comprehensive overview of MXene history, its properties, challenges, latest trends, and different applications to highlight its potential and gather new audiences towards this family of two-dimensional materials.
Development Of Bulk Thermoelectric N-type SiGe Alloy By Laser Powder Bed Fusion
Authors: Baudry Maxime , Savelli Guillaume , Roux Guilhem
Published: November 2024

Nowadays, Additive Manufacturing (AM) has revolutionised current production methods in many areas like aeronautics, military or medicine. Among these methods, Laser Powder Bed Fusion (L-PBF) is prevalent to printing complex metallic parts for small and medium series. Recent studies in L-PBF processing develops the production of new materials via this process, including thermoelectric (TE) materials. This study presents the manufacturing of silicon-germanium alloy by L-PBF, a TE material intended for high temperature applications. It is the first time that this material is manufactured by AM technology. Several dense samples were produced, and a first process window was identified. Structural analyses have been performed, highlighting very good densification but unfortunately mechanical cracking.
In-situ Heat Treatment Of FeTiB2 High Modulus Steel By Additional Laser Exposure During L-PBF
Authors: Tönnißen Nicklas , Hussain Shohag , Uhlenwinkel Volker , Springer Hauke
Published: November 2024

Additive manufacturing of Fe-Ti-B high modulus steels using the laser powder bed fusion (L-PBF) combines innovative processing technology with novel alloy design to enable next generation lightweight design solutions. By the inherent rapid solidification and in-process precipitation an even distribution of nanometer-sized TiB2-particles in a a-matrix is achieved, but porosity and cracks can only be eliminated by a substantial high substrate preheating for FeTiB2 (15 vol.%). Here we demonstrate how the substrate preheating temperature can be substantially reduced by use of intermittent laser exposure between layer depositions for FeTiB2 (12 vol.%). Hence, the molten surface is treated in a second exposure step with a reduced laser power (i.e. 25 – 75 %) as an in-situ heat treatment, aiding in the transformation of brittle metastable compounds to the equilibrium constituent’s ferrite and TiB2. These are not only desirable for improving the stiffness|density ratio, but also exhibit much less susceptibility for cracking.
Metal Powder Extrusion Of Large, Thin-walled Stainless Steel Structures At Room Temperature
Authors: Sorea Alexandru , Valler Peter , Lyck Christian
Published: November 2024

Metal powder extrusion was developed to manufacture steel components longer than 300 mm with a complex internal geometry and a wall thickness below 0.4 mm. These unique structures can be combined with customized alloys to facilitate innovation in many different industries. Extrusion of metal powders requires a compound that is flowable and has a high wet strength at room temperature. The right compound mixture and properties were obtained through the systematic method, Design of experiments. Sintering of extrudates introduced many new challenges, some of these were overcome with the help of sintering simulations and thermodynamics modelling of phase changes during sintering. This paper will present how to extrude and sinter such long, thin walled and complex shaped components through innovative and novel solutions and discuss the possible geometries, alloys and applications within heat exchanging, crash absorption and filtering.
Feasibility Of Titanium-based Materials For PEMFC Bipolar Plates Using Powder Metallurgy And Surface Modification Approaches
Authors: Romero Carlos , Benedetto Davide , Gordo Elena
Published: November 2024

Bipolar plate (BP) materials and designs are critical for the performance of a PEMFC and a PEMEC due to their role as reactant and product distributor and electron transporter between cells. With the goal of increasing the power density of the PEMFC stacks, especially for transportation, the weight of the bipolar plate is also an important parameter. Titanium is a material that is a promising alternative to stainless-steel to manufacture light, metallic-based BP if some of its challenges are addressed, one of them being the passivation of its surface during operation, that creates ohmic losses. The aim of this work is to assess the use of powder metallurgy to manufacture titanium-based bipolar plates with the ability to obtain alternative designs for the flow field and the use of suitable surface modification techniques that can improve the performance.
Metal|glass Interface Characterisation Of A Multiscale Bioactive Surface Structure On Ti-6Al-4V Alloy With Laser DED Process
Authors: Liu Yijun , Triantaphyllou Andrew , Eustice David , Ireson Robert , Holcroft Chris , Glendenning Malcolm
Published: November 2024

The present study demonstrates the feasibility to fabricate a multiscale bioactive surface structure onto a biomedical grade Ti-6Al-4V alloy substrate using a multi-material blown powder laser Direct Energy Deposition process (DED). The multiscale surface structure consisted of two layers: a Ti-6Al-4V transition layer with a customised structure, deposited onto a Ti-6Al-4V alloy substrate, followed by a layer of customised bioactive glass cladded on top. It is possible to create a transition layer with physical interlocking features that are fully bonded with the bioactive glass for enhancement of the metal-glass adhesion. The metal|glass interface was characterised in terms of metallurgical reactions and mechanical properties. Indentation tests confirmed excellent cohesion of the metal-glass interface. The microhardness of the bioactive glass near the interface varied from 5.44 to 7.78 GPa. Fracture toughness of the cladded glass was estimated in the range of 1.40-3.91 MPa m1|2.
Numerical Modeling And Experimental Study Of Swirling Supersonic Gas Flow In The EIGA Atomizer For Metal Powder Production
Authors: Qaddah Baraa , Chapelle Pierre , Bellot Jean Pierre , Jourdan Julien , Rimbert Nicolas , Deborde Agathe , Hammes Raphael , Franceschini Aurélie
Published: November 2024

The requirement of high-quality metal powders production with fine spherical particle size is growing rapidly for the metal additive manufacturing process. An attractive technique to produce such powders is the EIGA process (Electrode Induction melting Gas Atomization), which employs a swirling supersonic gas jet flow exiting a free-fall nozzle to atomize a molten metal stream. The gas dynamics has dominant influences on the atomization mechanisms.A numerical model is developed to simulate the gas flow behaviour through and downstream the EIGA nozzle. The results produced by the numerical model are consistent with experimental observations of the shock|expansion waves produced in the gas flow obtained using Schlieren optical technique.
Thermal Stability In Al-Mn-Cr-Zr Based Aluminium Alloys Tailored For Powder Bed Fusion -- Laser Beam
Authors: Mehta Bharat , Nyborg Lars , Frisk Karin , Bengtsson Sven , Hryha Eduard
Published: November 2024

Al-Mn-Cr-Zr family of alloys tailored for powder bed fusion – laser beam process have been developed by the authors. The alloys were designed by leveraging negligible solidification range close to solidification, leading to an "inherently crack free" alloy system. These alloys have been designed to benefit from higher amount of solutes in solid solution, which leads to stronger precipitation hardening via direct ageing to achieve high strengths. Since the alloying elements were selected having low bulk diffusivities, slower precipitation kinetics is expected which suggests retention of high strength even after secondary ageing post peak hardening. Upon secondary ageing the alloys at 523K for 2544 hours and 623K 1054 hours negligible hardness loss at 523K and 17 HV loss at 623K was observed. This was benchmarked against Scalmalloy® which was seen to have negligible hardness loss at 523K and 28 HV loss at 623 K respectively.
Powder Flow Analysis For Industrial Metallic Additive Manufacturing Directed Energy Deposition: Three Different Optical Approaches To Visualize The Powder Behavior
Authors: Alleaume Clovis , Rey Rodriguez Pilar , Castro Regal Gemma , Lázaro Martínez Alejandro , Sanchez Cruz Raúl , Prieto Río Camilo
Published: November 2024

Powder characteristics are important factors affecting the quality of metallic Directed Energy Deposition (DED) process. To improve the DED reliability, we have studied the behaviour of the powder and the gas that are expelled from the laser head nozzle. In order to do so, three different optical setups have been developed and used, allowing us to visualize the particle distribution in space, to determinate the speed and trajectory of individual particles, and to visualize the gas behaviour interacting with those particles. Those setups were used while changing different process parameters: powder composition (metals, ceramic, and mixtures of those), mass flow (grams|min) and gas flows (carrier & protection). A series of experimentation have been performed to ensure independent and quantified changes of each parameter. The obtained results will be presented, and the implication on a theoretical tolerance roadmap for industrial application will be discussed.
Development Of A Two-material Ti64|Ta Part By Pressing And Sintering For Biomedical Applications
Authors: Mihalcea Elena , Bouvard Didier , Alvarado-Hernández Francisco , Jimenez Omar , Olmos Luis
Published: November 2024

This works presents the fabrication of a two-layer material composed of a porous Ta core and a dense Ti6Al4V (Ti64) shell by pressing and sintering. It is part of a research project that aims at fabricating multimaterial bone implants that will allow a faster osseointegration. The sintering behavior of two-layer samples is studied by dilatometry. The interface bonding between the Ti64 and Ta layers is analyzed by SEM. Two layers are clearly obtained with a bonding developed by the solid state diffusion of Ta particles into Ti64 during sintering. The mechanical properties of the component are mainly dominated by the porous layer showing a wide pore size distribution, which should contribute to improve the cell and bone growth. The density of such materials is much lower than the one of pure Ta. It is concluded that hybrid materials can improve the response to osseointegration.
Fabrication Of Tailored Ti-based Materials By Conventional Powder Metallurgy For Bone Implant Applications
Authors: Bouvard Didier , Olmos Luis , Jimenez Omar , Chavez Jorge , Macías Rogelio
Published: November 2024

This works proposes a methodology for fabricating materials with specific characteristics tuned for replacing human bones. A Ti64 alloy powder is used as the base materials and it is mixed with Ag, Ta, TiN and salt particles to obtain different features. A knee-bone like component is fabricated, including a highly porous core of Ti64|25Ta|5Ag and compact outer of Ti64|5Ag that is supposed to improve corrosion and osseointegration. Besides, a harder top surface in Ti64|10TiN composite should increase the wear resistance. The green component is sintered at 1260°C in argon. Its stiffness is close to the one of bones thanks to the added porosity, which also provides a permeability close to the one reported for trabecular bones. Tribocorrosion behavior in simulated body fluid is improved by TiN addition. In conclusion, the proposed processing route is able to produce complex components fulfilling specific features required for human bone replacement.
Metal Binder Jet 3D Printing Using Water-atomized Powders.
Authors: Kinai Yuta , Osada Toshiko , Kobayashi Satoshi , Takahashi Tomo , Kato Yoshiyuki , Yokoyama Kenji
Published: November 2024

Binder jet printing has a characteristic of high modeling speed. Water-atomized powders with relatively low cost can be used for the binder jetting process. The use of fine powders is necessary to improve the density and strength of sintered bodies. In this study, green and sintered bodies were fabricated using water-atomized fine powders to improve the density and strength of sintered bodies.
Dynamic Modelling Of A Powder Compaction Cycle For A Hydraulic Press In The Sintered Components Production
Authors: Ganthaler Elias , MoradiMaryamnegari Hoomaan , Peer Angelika
Published: November 2024

The manufacturing process of sintered components requires the compaction of metal powder in a rigid die, performed for example by a hydraulic powder press. This paper presents a novel, fully coupled model combining a physical hydraulic system model and a Finite-Element-based (FE-based) compaction model to simulate a full press cycle of a powder compaction press. The first model calculates the piston's position by modelling the hydraulic circuit including the valves, hoses, and double-acting cylinders as well as the low-level controller. The piston positions are then passed as input to an FE-based software that implements an adapted multi-surface constitutive model for granular media. This allows to investigate the influence of different trajectories and controllers. In contrast to literature, the fully coupled model allows the simulation of the whole press-cycle instead of the compaction phase alone.
Microstructure And Mechanical Properties Of Additively Manufactured Pearl® Micro AD730®
Authors: Vives Solange , Mayer Charlotte , Després Arthur , Martin Guilhem , Veron Muriel , Blandin Jean Jacques
Published: November 2024

While superalloys such as IN718 have been successfully used to build complexe parts in AM, applications requiring higher service temperatures necessitate the development of alloys with increased capability. AD730® was developed as a C&W alloy with increased capability relative to wrought IN1718.This work first reveals the impact of minor elements B and Zr on LPB-F processed AD730® (promotion of solidification cracking), and the role of B regarding rupture creep resistance.The as built microstructure is completely different from the as forged alloy. This work shows how heat treatment allows to tune the microstructure to address either high fatigue and mechanical resistance, or better creep needs. Compared to AM IN718, AM AD730® shows the desired improvement in temperature capability, analogous to that in the forged version. Still, differences between AM and cast and wrought AD730® are attributable to differences in grain size and gamma prime (?’) precipitates distribution.
Effect Of Powder Batches And Laser Power On The Microstructure And Properties Of As-built And Heat-treated Laser Powder Bed Fusion CuCrZr Samples
Authors: Baffie Thierry , Roux Guilhem , Flament Camille , Soulier Mathieu , Pellat Michel , Salvan Claudia , De Vernon Claudie
Published: November 2024

Recently, we showed that >99% dense CuCrZr parts can be produced by Laser Powder Bed Fusion (L-PBF) process using a large power range (270 to 480W) [1,2]. The as-built (AB) microstructure is anisotropic showing columnar grains aligned along building direction (BD). After a solution annealing and age hardening (SA+AH), solidification cells disappear and the dislocations density decrease, whereas partial recrystallization, twins and Cr nano-precipitates are observed. Even if the microstructure is not fully similar to wrought CuCrZr one, yield strengths are equivalent. This work aimed to develop further the process by: (i) evaluating the impact of incoming powders and lasing parameters on the AB microstructure, (ii) analyzing the microstructural effects of SA+AH and (iii) comparing the mechanical, thermal and electrical properties in both conditions for three powders.[1] C.Salvan et al., Proceedings EuroPM2019, Oct.13-17 2019[2] C.Salvan et al., Mat. Sci. & Eng. A 826 (2021) 141915
Evaluation Of The Impact Of Thermal Strain Hardening On The Precipitation Of Strengthening Phases During L-PBF Manufacturing Of A Model Aluminum Alloy: Towards The Definition Of An Alloy Grade Designed
Authors: Toualbi Louise , Le Bouar Yann , Fossard Frederic , Mérot Jean-Sébastien , Orlacchio Federico , Stricot Pauline , Bahcelier-Locq Agnès , Horezan Nicolas , Boivin Denis , Davoine Cécile , Thomas Marc
Published: November 2024

The L-PBF process features very short interactions between the powder and the laser, resulting in very high solidification and cooling rates. During thermal cycling in L-PBF processing, phase precipitation and thermal strain hardening occur concomitantly, thus leading to high dislocation density correlated with anchoring to precipitates. It is therefore important to understand and control precipitation kinetics with respect to the thermal strain hardening phenomena generated by the thermal cycles of the L-PBF process. This issue concerns structural hardening aluminium alloys.The aim of this study is to understand the thermal, metallurgical and mechanical phenomena generated during the manufacture of a model aluminium alloy (Al-4Fe) by L-PFB, in order to evaluate the impact of thermal strain hardening on the precipitation of the strengthening phases. A fine microstructural characterization using scanning electron microscopy and transmission electron microscopy shows a strong the interaction between dislocation density and precipitation.
Efficient Modeling Of Primary And Secondary Atomisation In Close-coupled Gas Atomisers
Authors: Amatriain Aitor , Urionabarrenetxea Ernesto , Avello Alejo , José M. Martin
Published: November 2024

Computer simulation of metal powder gas atomisation aims to better understand the complex phenomena involved in the interaction between gas and liquid metal, in order to maximize productivity and to avoid common issues. An efficient axisymmetric simulation of primary and secondary atomisation is proposed, which reduces calculation time in conventional desktop computer to the range of few hours. Primary atomisation is modeled using a Eulerian model that predicts the gas|liquid ratio in the neighborhood of the melt delivery tube. The secondary atomisation uses a Lagrangian particle tracking approach with a multimodal breakup model to predict particle breakup, and thus particle size distribution. Transition from the primary to the secondary atomisation takes place at the iso-surface of void fraction equal to 90%, which is adopted as injection surface. Particle size distributions of gas-atomised copper powder obtained with simulations are compared with experimental results.
Increasing The Fine Particle Content In Metal Powders For LPBF Through Nanoparticle Dry-coating
Authors: Gärtner Eric , Mädler Lutz , Uhlenwinkel Volker
Published: November 2024

In powder-bed-based additive manufacturing (AM) processes, such as laser powder bed fusion (LPBF) typically the fine particles (less than 20 µm) are removed from metal powders in order to decrease powder cohesion that often results in inhomogeneous powder spreading. Nanoparticle dry-coating effectively reduces particle adhesion and allows for direct usage of the fine particles. A gas-atomized Cr25Co25Ni25Fe25 powder (less than 90 µm) with varying fine content was dry-coated with SiO2 nanoparticles (13 nm) in increasing concentrations up to 50 ppm. Measurements of flowability (dynamic angle of repose) and powder packing (Hausner-ratio) indicated a better processability of dry-coated powders upon nanoparticle addition. Nanoparticle dry-coated metal powders with a fine particle content of 20 vol.% showed a homogenous processing in a LPBF machine and a high relative part density >99.9%. The utilized fine fraction increased the powder yield, clearly highlighting the potential of dry-coating for AM technologies.
Effect Of Mo2C Additions On Grain Growth In NbC-Ni Cemented Carbides
Authors: Missiaen Jean-Michel , Labonne Mathilde , Lay Sabine , Lavigne Olivier , Garcia Luis
Published: November 2024

Cemented carbides are widely used for cutting and drilling tools. They usually combine a WC hard carbide phase and a Co-based ductile binder. NbC-Ni materials are considered as a possible alternative, especially for wear applications. The advantageous economic situation for raw materials sourcing, their interesting mechanical properties and low density have raised a new interest for these materials. However, mechanical properties can be limited by the rapid grain growth during liquid phase sintering, as compared to WC-Co. Grain growth can be controlled by the addition of secondary carbides such as Mo2C. In this paper, a quantitative EBSD analysis of grain growth is performed for NbC-12vol%Ni materials sintered at 1360°C with controlled addition of Mo2C. The average grain size decreases continuously with Mo2C content. The results are discussed based on a more detailed interface characterization and on a previous model for the cooperative migration of phase boundaries and grain boundaries.
Development Of Premixed Materials For Diamond Cutting Tools
Authors: Zanon Matteo , Kossakowski Darek , Mais Bernhard
Published: November 2024

As an alternative to pure cobalt, "prealloyed" powders have by now firmly established themeselves as metallic matrixes in the diamond cutting tools industry. While technically high performing, they must rely on an elaborated production process and face increasing supply chain pressure with regard to cobalt. Moreover, the low compressibility implies high green-to-sinter dimensional change, thus compromising the achievable dimensional precision via free sintering. A new family of cobalt-free premixed materials for diamond cutting tools was developed to fill such gaps. Pressing and sintering results will be presented for several grades; their interaction with syntethic diamonds and their degree of metallurgical bonding was studied as well.
Metal Powder Production Optimisation By Increasing The Inlet Gas Temperature
Authors: Bustamante Valencia Lucas , LONG Qianlei , ZHOU Yun , Mandou Quentin , Briand Francis , Januard Fabien
Published: November 2024

With the booming of additive manufacturing, metal powder manufacturers are facing a growing demand of gas atomized powder complying with very stringent technical specifications in terms of oxidation or particle size distribution (PSD).From a metal powder producer perspective, optimizing the PSD makes possible to be more selective in terms of targeted markets and results in a direct increase of profitability, also limiting waste and thus carbon footprint.Most of the atomization processes deal with a complex interaction between the metal and a gas jet. The literature of metal powder production stands for a narrowing of the particle size distribution with the optimization of the momentum of the gas jet. It could include the change of the flow, pressure and temperature of the inlet gas but also its composition, considering gas mixtures.This work presents results of trials conducted on an industrial gas atomization unit using nitrogen as gas stream to atomize
Additive Manufacturing Of Highly Efficient Electric Sheets Of Fe6,5Si By 3D Screen-Printing
Authors: Reuter Kay , Lindemann-Geipel Inge , Jin Zhengyi , Studnitzky Thomas , Andersen Olaf , Weißgärber Thomas , Koch Raphael
Published: November 2024

Energy-efficient electric motors are crucial for the progress of electromobility. Soft magnetic materials with a high silicon content, such as Fe6.5Si, offer the possibility of high electrical resistance, high saturation magnetization and comparatively low power losses. However, due to the brittleness of Fe6.5Si, this material cannot be processed using conventional manufacturing methods (such as stamping). By means of 3D screen printing process, this material can be processed through a powder metallurgical processing route. Thus, electric steel sheets with low thickness, high alloying content and high productivity can be realized. We present results of printed and sintered Fe6,5Si electric steel sheets with thicknesses between 100 and 350 µm. The power loss can be reduced below 35 W kg-1 at 1000 Hz and 1 T. The magnetic properties of the sheets will be discussed in dependence on the sintering parameters and the powder properties.
Laser Powder Bed Fusion Of High Carbon Tool Steels
Authors: Reijonen Joni , Antikainen Atte , Lagerbom Juha , Lindroos Matti , Pinomaa Tatu , Lindroos Tomi
Published: November 2024

Tool steels are martensitic steels alloyed with carbide forming elements, thus having high strength, hardness and wear resistance. These characteristics, however, make them costly materials to shape into complex geometries. Laser powder bed fusion (PBF-LB) enables the consolidation of near-net-shape complex shapes from powders, which is a highly resource efficient way of producing tools. However, processing tool steels with PBF-LB is problematic due to hardening and segregation generated during the process leading to high stresses and eventually to cracking. To diminish these problems, we utilized a tailored high temperature building platform in PBF-LB to process gas atomized high carbon tool steels such as K110 and S600. Calphad method was used to evaluate the stress formation and cracking tendency of these alloys. The microstructure, hardness and tendency to form residual stresses of the manufactured samples were characterised. Properties comparable to conventionally manufactured quenched and annealed tools steels were achieved.
Developing Competitive High Entropy Alloys By Selective Laser Melting Using Commercial Commodity Powders
Authors: Venkatesh Kumaran S , Torralba José Manuel
Published: November 2024

High entropy alloys (HEAs) have garnered significant research attention due to their unconventional alloying approach which results in exceptional properties. Recently, additive manufacturing processes like Selective Laser Melting (SLM) have been used to fabricate HEAs with enhanced mechanical properties. However, SLM processes demand the use of fully pre-alloyed powders since using elemental powders directly might lead to pronounced segregations. However, there are no readymade pre-alloyed HEA powders in the market and pure elemental powders are expensive. So, in this work, commercial commodity powders like Ni 625,CoCrF75, 316L, Invar36, and Fe49Ni which are readily available at competitive prices, were used to make HEAs. The selected powders were mixed in appropriate proportions and printed using SLM. The resultant alloy was a CoCrFeNiMox, with an FCC phase and exhibited promising mechanical properties. This work opens a completely new field of work with multiple possibilities to manufacture HEAs by additive manufacturing at competitive prices.
Comparison Of Milled And Blended Powder Mixtures On The Example Of AlSi10Mg With Different SiC-contents For The Processability In A L-PBF Process
Authors: Becker Malte , Ludwig Ina
Published: November 2024

Additive Manufacturing (AM) stands out in lightweight construction, material efficiency and geometric freedom. But as it is still a relatively young technology only a small number of alloys has been developed and thus there is a lack of material diversity especially for highly stressed AM components.One way to increase mechanical properties is using composite alloys that are reinforced by ceramic particles.Subject of this investigation are the effects of reinforcing AlSi10Mg with different volume fractions of silicon carbide (SiC), by either mixing or milling and the processability of the reinforced powder in a LPBF process.The used powders are characterized including optical inspection, particle size distribution, particle morphology and flowability. The manufactured parts analyzed regarding the density and tested for their mechanical properties. Based on the results correlations between the powder manufacturing process, alloy composition and mechanical properties are evaluated.
Static And Fatigue Behaviour On Powder Bed Additive-manufactured Hydraulic Component
Authors: Grosjean Christophe , Marzin Michel , Camus Etienne , Munch Thomas , Robert Maxime
Published: November 2024

Metallic additive manufacturing processes are now widely used in many sectors, leading to more and more data on "conventional" mechanical testings. This article deals with a hydraulic block used on construction and mining machines and aims to have a better understanding of the behaviour of additively manufactured parts undergoing high internal and cyclic pressure.First, a topology optimization was performed to reduce weight and take advantage of AM’s ability to produce complex geometries.Then, different mechanical exams were carried out on samples and a pressure test was done on each component.A comparison between a conventional part and an AM parts enabled to demonstrate the interest of topology optimization to reduce pressure drops.Finally, fatigue tests were used to evaluate the cyclic pressure resistance of the parts. These tests were completed by a calculation phase allowing to better understand the origin of the various identified initiation sites.
Densification And Microstructural Characterization Of WB4 Based Ultrahard Materials
Authors: Navarrete Cuadrado Jazmina , Soria Biurrun Tomas , Lozada Cabezas Lorena , Moseley Steven , Gonzalez Polvorosa Nerea , Tarragó Jose M. , Sanchez-Moreno Jose M.
Published: November 2024

Tungsten borides are potential candidates for the fabrication of tool materials. Among them, tungsten tetraboride is attracting increasing attention due to its very high hardness (» 47 GPa), good electrical conductivity and abrasion and corrosion resistance. Nevertheless, the technologies needed to obtain WB4 based usable tools are still to be developed. In this work, full densification of WB4 based hard materials has been achieved by applying glass encapsulated HIP cycles to powders mixtures with different W|B ratios and Ta additions. Contrary to that reported by other authors, it has been confirmed that Ta addition enhance the transformation of tungsten tetraboride (WB4) into tungsten diboride (WB2). Processing parameters have been tailored for retaining the hard WB4 hexagonal phase after sintering reaching hardness values over 26 GPa (HV5). Interaction between WB4 and different metals has been investigated in order to find suitable binder phases for producing tougher WB4-metal cermets.
New Approaches To Powder Production Using Conical Laser Beams
Authors: Chivel Yuri
Published: November 2024

A process is presented for obtaining a spherical powder in a wide range of sizes 50 nm - 50 µm, in which a continuous near-surface optical discharge with a temperature of 20 kK is formed using conical laser beams in an argon flow, into which material is introduced in the form of a wire. The condensation are strongly and rapidly quenched by an inert gas flow at atmospheric pressure, producing high supersaturation . The process capacity is 0.5 kg|kWh with a laser power of 10 kW.The process of nanoparticle formation using inert gas condensation of metal vapour produced by conical laser beam vaporization of micropowder 40-60 µm stream with a particle concentration of 104-106 cm -3 has been investigated. Experimentally obtained nanoparticles 20-50 nm are collected in the form of conglomerates up to 100 nm in size. The productivity of the process reaches 0.2 g | W h .
Laser Powder Bed Fusion Of Innovative Beta-Ti21S Cellular Structures For Biomedical Implant
Authors: Emanuelli Lorena , Jam Alireza , Lora Carlo , De Biasi Raffaele , Benedetti Matteo , Pellizzari Massimo
Published: November 2024

Development of innovative cellular structures fabricated by laser powder bed fusion (LPBF) of beta titanium alloy in the orthopedic implant fields are in continuous evolution. Recent studies highlighted the promising performances of ß-Ti21S alloy, namely low elastic modulus, extraordinarily ductility and high fatigue resistance that makes it competitive with respect to Ti6Al4V. Considering cellular structures, auxetic and Triply Periodic Minimal Surface (TPMS) structures have received great interest in the recent year. Auxetic structure is interesting to achieve very low elastic modulus and TPMS to promote osseointegration. Furthermore, recent studies propose cellular structures with a porosity gradient to combine mechanical performances and bone tissue growth. In this work manufacturability of auxetic and TPMS structures in ß-Ti21S alloy having 2.5 mm cell size and a porosity gradient inside the structures are investigated. Dimensional precision analysis comparing CAD with printed structures, microstructure characterization and defectiveness analysis of surface and bulk are carried out.
Development Of Sinter Hardening Material With High Bending
Authors: Hazama Takuya , Hara Jumpei , Takenaka Chihiro , Akiyama Yu , Uozumi Masato , Suganaga Kazuhiko
Published: November 2024

The use of sinter hardening material (SH material) was examined for the purpose of cost reduction by simplifying the part manufacturing process in our company, in response to the fact that many 4WD coupling cam parts adopt a sintering method that allows the cam shape to be formed with a net shape. The SH material has high hardenability, however it is not applicable for parts that require bending fatigue strength due to its low toughness. Accordingly, bending fatigue strength was improved and the required strength of the parts was successfully satisfied by achieving a mixed phase structure of martensite and austenite due to the addition of Ni to SH material.
An Experimental Approach To Acquire Material-specific Parameters To Simulate The Sintering Process In Binder Jetting, Using In-situ Gravitational Beam Bending Tests And Dilatometry
Authors: Greifzu Moritz , Peter Fabian , Tan Hong Tiat , Mehta Tarang Dineshchandra , Eckardt Joanna , Acharya Sohan , Marquardt Axel , Stepien Lukas , Lopez Elena , Brückner Frank , Leyens Christoph
Published: November 2024

Binder jetting (BJ) is a sinter-based additive manufacturing technology with several advantages over laser or electron beam-based powder bed processes. This includes faster build rates, non-necessity of support structures and no introduction of thermal stress into the part during the build. On the other hand, BJ parts shrink considerably during sintering making it more challenging to produce parts within tolerances. Recently, software to simulate and compensate this distortion has been commercialized. Since the algorithm is based on a phenomenological model, experiments have to be conducted to feed material parameters into this model for correct simulation of a specific alloy. Here, an experimental approach is presented using dilatometry and in-situ gravitational beam bending to perform a full characterization of stainless steel powder 316L , and the extraction of the relevant data for the simulation.
Influence Of Interstitials Content On Martensite Decomposition And Beta Transus Temperatures Of Ti-6Al-4V Built By Laser Powder Bed Fusion
Authors: Gaillard Quentin , Boulnat Xavier , Cazottes Sophie , Dancette Sylvain , Desrayaud Christophe
Published: November 2024

L-PBF made Ti-6Al-4V parts show a fine martensitic microstructure and significant residual stresses that are disastrous for their mechanical performance. Consequently, post-processing heat treatments are necessary to relieve the internal stresses and lead to a microstructure adequate for the mechanical requirements. Due to the various powder compositions and processing parameters, there is a large scattering of properties of as-built and stress-relieved parts. As such, this study aims at quantifying the link between interstitials (oxygen, nitrogen) contents and the transition temperatures (martensite decomposition, beta transus) of as-built parts and as-atomized pre-alloyed powders as a reference. To do so, high-temperature X-Ray diffraction, differential scanning calorimetry and electron microscopy were performed. This insight provides a guide for designing post-processing heat treatments of Ti-6Al-4V as-built parts.
Aging Of Sintered Ag Tracks And Die Attach Layers For Power Electronics Modules
Authors: Missiaen Jean-Michel , Botter Nicolas , Bouvard Didier , Avenas Yvan , Khazaka Rabih
Published: November 2024

An assembly for power electronics based on the deposition and pressureless sintering of successive silver layers on an Aluminum Nitride heat sink has been developed. Sintered silver layers act as die attach, current tracks and adhesion layer on the ceramic. This assembly has the advantage to give sintered joints with a high mechanical strength and a high thermal conductivity compared to standard brazing alloys at the highest operating temperature of semiconductor components (200°C). In this paper, aging of the silver tracks and die attach layers is studied. A significant coarsening of the microstructure is observed in confined areas, under the chip and|or far from the external surface, after 200h annealing in air at 200°C, whereas coarsening is essentially inhibited in argon atmosphere. The shear strength and thermal properties of the sintered joint are improved after thermal storage in air. Mechanisms of the microstructural evolution and microstructure-properties relationships are discussed.
Effect Of Process Control On The Densification Of Cr-prealloyed PM Steels Through Vacuum Sintering In Conjunction With Capsule-free Hot Isostatic Pressing
Authors: Nagaram Anok Babu , Hryha Eduard , Nyborg Lars , Gårdstam Johannes , Vattur Sundaram Maheswaran , Andersson Michael , Chen Zhuoer
Published: November 2024

In this study, compacts of Cr-prealloyed steel with admixed nickel and graphite, fabricated through cold isostatic pressing (CIP), were sintered in low vacuum at 1150 °C and at 1250 °C in a HIP furnace, followed by the capsule-free hot isostatic pressing (HIP) at 1150 °C in the same HIP furnace using argon at 100 MPa. Microstructures of these compacts sintered at 1250 °C revealed the complete closure of interconnected porosity, after which densification to full bulk density was achieved by final HIP stage. Hardness measurements and chemical analysis were also employed. Carbon as a reducing agent played a crucial part to reach very low oxygen content of 0.02% after sintering and capsule-free HIP. This study demonstrates the possibility of achieving full density in high performance powder metallurgy (PM) steels through novel approach of CIP and in-situ vacuum sintering in combination with capsule-free HIP using a two-stage densification process.
Heat Treatment And Properties Of AISI 415 Martensitic Stainless Steel Manufactured By Laser-Directed Energy Deposition
Authors: Amirabdollahian Sasan , Eslami Maryam , Bosetti Paolo , Perini Matteo , Molinari Alberto
Published: November 2024

Laser-directed energy deposition (L-DED) is one of the most practiced additive manufacturing (AM) methods that provide opportunities for the production of parts as well as repair and cladding. AISI 415 Martensitic stainless steel demonstrates high mechanical properties, excellent toughness, and weldability with a wide range of applications. In the current work, crack-free and full-dense parts were deposited after developing proper processing parameters. As-built (AB) microstructure comprised lath martensite with a microhardness of 400HV. The effect of two different heat treatment scenarios of direct tempering of the as-built part (DT) and austenitization and quenching prior to tempering (QT) on the microstructure and hardness were investigated. The tempering curves for the two scenarios were similar, demonstrating a hardening peak at 450°C, while DT samples possessed slightly higher hardness due to the finer martensite substructure. Polarization tests revealed AM sample demonstrates 110 mV higher pitting potential compared to the conventional.
Micromechanical Modelling Of Additively Manufactured High Entropy Alloys To Establish Structure-properties-performance Workflow
Authors: Laukkanen Anssi , Suhonen Tomi , Metsajoki Jarkko , Andersson Tom , Lindroos Matti , Ge Yanling , Vallejo Rodríguez Luis
Published: November 2024

Additive manufacturing is a manufacturing route able to produce complex components with minimal raw-material utilisation and high-level of process control. However, the rapid solidification rates, strong temperature gradients and extremely localised melting lead to non-equilibrium microstructures that require a better understanding of solid-state transformation, solidification behaviour and structure-property-performance workflow of AMed materials. HEAs unique compositions and complex microstructures slow down considerably the AM parameter optimisation of these materials. Numerical simulations offer a better understanding of the structure-properties-performance of the materials with a reduced number or physical experiments. Hence, a multi-scale modelling approach is taken. For the alloy design phase, Calphad analysis together with DFT simulations and machine learning tools are used to find the most promising HEA compositions. Studying the different microstructural defects, deformation mechanisms that affect the strain hardening potential and damage susceptibility, Crystal-Plasticity models are developed to evaluate the performance of AMed HEAs and the overall workflow.
Brief Review on Fermentation Process and Food Additives
Authors: Popova Yanka Dimitrova , Dimitrova Еma Yordanova , Iglicina Maria Yordanova
Published: November 2024

People’s interest in healthy eating and quality food is growing these days. There are various sources through which we learn about the advantages and disadvantages of foods, their benefits and some of their harmful effects on humans. Since school, young people are excited and discuss topics related to the composition of food and the role of its components - fats, carbohydrates and proteins. Theirstructure and properties are studied in the subject Chemistry and environmental protection in the profiled classes. The obtained theoretical knowledge is a basis on which young people form a culture of nutrition, striving to be healthy and energetic. More and more of them choose to continue their studies in specialties related to nutrition. The aim of the present study is to present knowledge from the field of Food Chemistry that is useful for human health. Food chemistry is an evolving discipline studying the chemical processes and interactions of all biological and non-biological components in foods. Foods are a complex combination of chemicals, many of which are vital to our survival. An important part of food content are food additives such as emulsifiers, food colourings, flavourings and preservatives, the main characteristics of which will be presented in the article. Examples of food additives and sweeteners that are harmful to human health are also given. The experimental part of the article describes fermentation as a chemical technology, as well as the importance of alcoholic, acetic acid and lactic fermentations. As an expected result, information about chemical technologies and food additives in food will enrich the knowledge of adolescents on the one hand, and on the other hand, will be beneficial for their proper development and good health. In addition, students can focus on studying food chemistry and realize themselves professionally in this field.