Additive Manufacturing Materials Research Articles

A review on 4D printing: Material structures, stimuli and additive manufacturing techniques

Advances in 3D printable smart materials are leading to the development of four-dimensional printing (4DP). Assembling stimulus-responsive materials and combining their functionalities into a single printed construct is an efficient way to improve the shape recovery capability of the smart structure. Three types of multi- material structures are reported in the literature: uniform distribution, gradient distribution, and special patterns. Smart materials have the unique property of changing their shape and properties when activated by external stimuli such as heat, water, or pressure. This article provides an overview of current smart material structures, types of stimuli, and three-dimensional printing (3DP) technologies used to manufacture 4D smart structures.

A Review of Particle Size Analysis with X-ray CT.

Particle size and morphology analysis is a problem common to a wide range of applications, including additive manufacturing, geological and agricultural materials' characterisation, food manufacturing and pharmaceuticals. Here, we review the use of microfocus X-ray computed tomography (X-ray CT) for particle analysis. We give an overview of different sample preparation methods, image processing protocols, the morphology parameters that can be determined, and types of materials that are suitable for analysis of particle sizes using X-ray CT. The main conclusion is that size and shape parameters can be determined for particles larger than approximately 2 to 3 μm, given adequate resolution of the X-ray CT setup. Particles composed of high atomic number materials (Z > 40) require careful sample preparation to ensure X-ray transmission. Problems occur when particles with a broad range of sizes are closely packed together, or when particles are fused (sintered or cemented). The use of X-ray CT for particle size analysis promises to become increasingly widespread, offering measurements of size, shape, and porosity of large numbers of particles within one X-ray CT scan.

Compression Tests at High Strain Rate on 3D-Printed CuCrZr Alloy Specimens - Material Model Calibration

CuCrZr alloy is used to produce actively cooled components for high heat flux elements of beamlines and for heat sink of plasma facing components in nuclear fusion devices such as ITER and DEMO. It has an excellent thermal conductivity and specific mechanical strength, together with a high electrical conductivity that is giving high push to its use. Recently, CuCrZr alloy was also considered as an attractive material for Additive Manufacturing, leading to extend its application in the field of strain rate studies. As a matter of fact, its strain rate dependency is playing an important role for vertical target plasma-facing units components uses as heat sink in the ITER divertor or as structural material for actively cooled plasma facing components. This paper describes the results obtained by quasi-static and dynamic compression tests carried out on CuCrZr specimens produced by laser Powder Bed Fusion (PBF), with Selective Laser Melting (SLM) technology. Quasi-static tests have been conducted by means a servo-hydraulic tensile machine, while a direct tension-compression split Hopkinson bar has been used to perform the tests at high strain rate. Since dedicated heat treatments are required to obtain optimal combination of strength, ductility, and conductivity, some of the specimens have been heated up to 560 – 580 °C for 4 – 5 h and then cooled in air. Eventually, the calibration of the most appropriate constitutive models for 3D-printed CuCrZr alloy deformed at high strain rate has been carried out by means an inverse analytical procedure.

Effect of Surface Polishing on Physical Properties of an Occlusal Splint Material for Additive Manufacturing under Protection Gas Post-Curing Condition.

The aim of this study was to evaluate the effect of surface polishing as well as the post-curing atmospheres (air and nitrogen gas) on the physical properties of an occlusal splint material for additive manufacturing. Flexural strength, flexural modulus, Vickers hardness number (VHN), degree of carbon double bond conversion (DC), water sorption (WSP), and water solubility (WSL) were evaluated. Surface polishing significantly affected the evaluated properties. Regardless of the post-curing atmosphere, flexural strength, flexural modulus, VHN, and DC showed significantly higher values for the polished specimens when compared with the unpolished ones, while WSP and WSL were significantly lower for the polished specimens. Unpolished specimens post-cured at nitrogen gas showed significantly higher VHN and DC values. However, the effect of the post-curing at a nitrogen gas atmosphere was non-significant in polished specimens. The current results suggested that surface polishing plays a role in the physical properties of the evaluated occlusal splint material and can enhance all the evaluated properties regardless of the post-curing atmosphere. Meanwhile, the post-curing at a nitrogen gas atmosphere can enhance the VHN and DC but its effect is confined only to the surface layers, which can be removed during surface polishing.

High-temperature failure and microstructural investigation of wire-arc additive manufactured Rene 41

In developing a wire-arc plasma direct energy deposition process for creep-resistant alloys used in high-speed flight applications, structures were built from nickel-based superalloy Rene 41. Samples of additive manufacturing (AM) material were analysed for their microstructural and mechanical properties, in both as-deposited (AD) and heat-treated (HT) conditions. Tensile specimens were tested at room temperature, 538, 760, and 1000 °C. Macroscopically, large columnar grains made up of a typical dendritic structure were observed. Microscopically, significant segregation of heavier elements, grain boundary precipitates, and secondary phases were observed, with key differences observed in HT material. There was a clear distinction between failure modes at different testing temperatures and between AD and HT variants. A fractographic investigation found a progressive move from brittle to ductile fracture with increasing testing temperature in both AD and HT conditions, as well as microstructural features which support this observation.

Lignin-Based Materials for Additive Manufacturing: Chemistry, Processing, Structures, Properties, and Applications.

The utilization of lignin, the most abundant aromatic biomass component, is at the forefront of sustainable engineering, energy, and environment research, where its abundance and low-cost features enable widespread application. Constructing lignin into material parts with controlled and desired macro- and microstructures and properties via additive manufacturing has been recognized as a promising technology and paves the way to the practical application of lignin. Considering the rapid development and significant progress recently achieved in this field, a comprehensive and critical review and outlook on three-dimensional (3D)printing of lignin is highly desirable. This article fulfils this demand with an overview on the structure of lignin and presents the state-of-the-art of 3D printing of pristine lignin and lignin-based composites, and highlights the key challenges. It is attempted to deliver better fundamental understanding of the impacts of morphology, microstructure, physical, chemical, and biological modifications, and composition/hybrids on the rheological behavior of lignin/polymer blends, as well as, on the mechanical, physical, and chemical performance of the 3D printed lignin-based materials. The main points toward future developments involve hybrid manufacturing, in situ polymerization, and surface tension or energy driven molecular segregation are also elaborated and discussed to promote the high-value utilization of lignin.

Mechanical Properties of PLA Specimens Obtained by Additive Manufacturing Process Reinforced with Flax Fibers

Although polylactic acid (PLA) is one of the most used materials in additive manufacturing, its mechanical properties are quite limiting for its practical application, therefore, to improve these properties it is frequent to add fibers and, in this way, create a more resistant composite material. In this paper, the authors developed PLA composites reinforced with flax fibers to evaluate the improvement of tensile and flexural strength. The experimental design of experiments was based on the L18 Taguchi array where the control factors were the extruder temperature (three levels), number of strands (three levels), infill percentage of the specimens (three levels), and whether the flax fiber had surface chemical treatment. The tensile and flexural specimens were made on a 3D printing machine and was a mold was developed to fix and align the fiber strands during the printing process. The tensile and flexural experimental tests were performed in agreement with ASTM D638.14 and ISO 14125 standards, respectively. Analyzing the results, it was verified that the surface chemical treatment (NaOH) of the fiber did not show any influence in the mechanical properties of the composites; in contrast, the infill density demonstrated a huge influence for the improvement of mechanical strength. The maximum values of tensile and bending stress were 50 MPa and 73 MPa, respectively. The natural fiber reinforcement can improve the mechanical properties of the PLA composites.

The Processing Map of Laser Powder Bed Fusion In-Situ Alloying for Controlling the Composition Inhomogeneity of AlCu Alloy

In-situ alloying is a facile method for exploring high-performance metallic materials for additive manufacturing. However, composition inhomogeneity is inevitable, and it is a double-edged sword for the properties of in-situ alloyed parts. Appropriately controlling the composition inhomogeneity benefits the applications of in-situ alloying in specific microstructural and properties design. In this work, the Al20Cu alloy was selected as the benchmark alloy to investigate the tailoring of composition inhomogeneity. The morphology and area percentage of composition inhomogeneity in the as-built samples were firstly analyzed. These results provided evidence for the formation of composition inhomogeneity and indicate that its content is tightly dependent on processing parameters. The characteristics of the molten pool under various processing parameters were investigated by modeling the laser remelting process. Based on these, a processing map was established to guide the tailoring of composition inhomogeneity. This study expands the understanding of the formation mechanism of composition inhomogeneity in in-situ alloyed parts and sheds light on employing laser powder bed fusion in-situ alloying for new materials development.

Laser powder bed fusion technique of hydrogen–fueled gas turbine: Role of advanced materials and its challenges

Aviation accounts for 1.9% of greenhouse gas emissions, decarbonization is not straightforward as electrification is not feasible, and biofuels only partially address the issue. Therefore, aero-engine manufacturers are looking towards hydrogen as a clean fuel source as the emissions would majorly be water with no lasting greenhouse gasses. The major challenge with hydrogen-firing engines would be high firing temperatures, corrosive exhaust gasses and adverse reactions with structural components. The design flexibility of additive manufacturing (AM) and advanced materials development, such as high entropy alloys (HEAs) can be combined to produce gas turbines with higher turbine inlet temperatures and power output. This paper discusses the advantages and issues with hydrogen as fuel, the role of AM and advanced materials suitable for hydrogen-firing engines.

Additive Manufacturing Service Provider Selection Using a Neutrosophic Best Worst Method

Additive manufacturing (AM) is poised to disrupt the manufacturing industry due to its distinctive (layer-by-layer) approach to part production, as AM comprises a range of fabrication techniques that facilitate the production of customized and highly complex parts. For a particular part selecting the most suitable AM machine and material is an indispensable decision due to several AM machines, their process and material constraints like size, accuracy, mechanical properties etc. This paper demonstrates the multi-criteria framework using Delphi and neutrosophic best-worst method to determine the best suitable AM machine and feasible material from the spool of databases. The Delphi method is employed to determine and validate essential criteria for a selected part, which results in shortlisting the 9 most relevant criteria. Further, the neutrosophic best-worst method is utilized to compute the criteria weights. A rating and normalization approach is deployed to calculate each AM machine and compatible material aggregate score to determine the optimal AM machine, material and ultimately, the AM service provider.

Mechanical properties of stainless steel by using high temperature microhardness tester

In the aeronautical field, materials are used in severe environmental conditions (temperature, atmosphere), particularly for engine applications. In order to qualify new alloys compositions, ONERA is developing micromechanical characterization means to carry out indentation tests from room temperature up to 700 °C under conditions close to operating conditions. This method presents the interest of performing tests faster than classical mechanical tests like tensile or bending tests under severe conditions and with small amounts of materials. In order to carry out screening tests, a 316L stainless steel is studied and the evolution of hot Vickers hardness properties and yield stress versus temperature are presented. By increasing the applied load from 0.1 to 20 N, we show that we can neglect surface microstructural changes or possible contamination of the sample surface by oxidation. We show that from 0.5 N, the hardness measurement is independent of load on 316L stainless steel. By using Tabor’s law to express the mechanical resistance, we show that the hardness decreases by 50% when the test temperature goes from 20 to 700 °C, which is close to the supplier’s values. A discussion on the use of indentation to determine mechanical resistance and the limitations of this technique is presented. In perspective, these measurements could be carried out at 1000 °C and on many different materials such as layers, coatings, composite materials, brazing cords or additive manufacturing materials.

A Study on the Fatigue Life of the Laser Additive Manufactured Metallic Material

As more and more structural parts of military aircraft are formed with additive manufacturing (AM) technology, it was very urgent to study fatigue characteristics of additive manufacturing materials and structures. In order to study the fatigue life characteristics of aluminum alloy and titanium alloy manufactured by selective laser melting (SLM), a series of specimens with various structural details were designed and tested under constant amplitude and random spectrum. The basic reliability life of each test results was statistically analyzed and the reliability safety life curve was obtained. Fractography analysis showed that there were more defects and mixed failure characteristics in aluminum alloy specimens, while the fatigue-scatter of titanium alloy counterpart was larger than that of forgings.

Simulation of powder spreading of functionally graded materials in powder bed fusion additive manufacturing

Simulation of powder spreading of functionally graded materials in powder bed fusion additive manufacturing

Innovative Technologies for Sustainable Recycling and Re-manufacturing of Materials and Components

The increasing demand for sustainable manufacturing and recycling processes has driven the development of innovative technologies to address the challenges associated with the re-manufacturing and recycling of materials and components. This research paper presents a comprehensive review of the latest advancements in sustainable recycling and re-manufacturing technologies, with a focus on their potential to reduce environmental impact, enhance resource efficiency, and promote circular economy principles. We explore cutting-edge technologies such as additive manufacturing, smart disassembly, and advanced material separation techniques, which have shown promise in enabling efficient recycling and re-manufacturing of materials and components. Additionally, we investigate the integration of digital technologies, including the Internet of Things (IoT), machine learning, and blockchain, to optimize recycling and re-manufacturing processes. Our analysis reveals that these technologies can significantly improve the quality and efficiency of recycled and re-manufactured products, reduce waste generation, and minimize energy consumption. Furthermore, we discuss the potential economic and environmental benefits of adopting these technologies, as well as the challenges and barriers to their widespread implementation. The findings of this research provide valuable insights for policymakers, industry stakeholders, and researchers working towards the development and adoption of sustainable recycling and re-manufacturing technologies.

Towards a Circular Economy: Challenges and Opportunities for Recycling and Re-manufacturing of Materials and Components

The transition towards a circular economy is a critical step in achieving sustainable development and mitigating environmental degradation. This study explores the challenges and opportunities associated with recycling and re-manufacturing of materials and components within the context of a circular economy. We conducted a comprehensive analysis of the current state of recycling and re-manufacturing technologies, identifying key barriers such as material degradation, contamination, and technological limitations. We also examined the potential for innovative solutions, including advanced material characterization techniques, additive manufacturing, and digital twin technologies, to address these challenges. Our findings reveal that the integration of these technologies can significantly enhance the efficiency and effectiveness of recycling and re-manufacturing processes, enabling the recovery of high-quality materials and components. Furthermore, we highlight the importance of establishing a robust regulatory framework and incentivizing industry participation to accelerate the transition towards a circular economy. This study provides valuable insights for policymakers, industry stakeholders, and researchers working towards the development and implementation of sustainable materials management strategies. By addressing the challenges and harnessing the opportunities identified in this study, we can pave the way for a more sustainable and resource-efficient future.

Materiales más usados en fabricación aditiva en el sector metalmecánica: Una revisión sistemática

La fabricación aditiva o conocida también como impresión 3D es un gran avance que se ha desarrollado en la producción industrial permitiendo que los tiempos se reduzcan, para ello es importante conocer sus procesos, por lo que se realizó esta revisión sistemática que tiene como pregunta: ¿Qué materiales y técnicas son las más usadas en el sector de metalmecánica? De modo que nuestro objetivo de investigación es describir los resultados de los materiales más usados en esta industria, tecnologías, técnicas y aplicaciones. Esta búsqueda se logró gracias a revisión de artículos publicados en base datos como ScienceDirect,Vtindustrial, Redalyc, ResearchGate, Nature, Semantic Scholar, Sciendo, Resiup, Oikonomics, IOPScience, HAL, Core comprendida entre los años 2017 al 2022.

UNCONVENTIONAL METHODS OF MANUFACTURING THIN WIRES FOR APPLICATION AS INPUT MATERIAL IN ADDITIVE MANUFACTURING. PART 2: DRAWING OF Fe-BASED ALLOY WIRES

The article presents the technology of drawing thin wires made from selected iron-based alloys for use in additive manufacturing using WAAM method. The final technology of wire production was developed with the use of a drawing bench, depending on the deformed material. Steel wires with a diameter of 1 mm and mechanical properties adapted to the 3D printer were produced.

UNCONVENTIONAL METHODS OF MANUFACTURING THIN WIRES FOR APPLICATION AS INPUT MATERIAL IN ADDITIVE MANUFACTURING. PART 1: PREPARATION OF INPUT MATERIAL FOR WIRE DRAWING

Part 1 of the article presents the technological path of producing semi-finished products for wires constituting input material in additive technologies. On the basis of the developed chemical compositions of experimental Fe-based alloys, laboratory ingots with a square section of 120×120 mm / 130×130 mm were produced, which were then hot rolled into flat bars. In order to select the physical parameters of the drawing tests, numerical modelling of the process was performed. As a result of the simulations, it was found that the calculated drawing force exceeds the capabilities of the experimental drawing machine and for this reason, hydrostatic extrusion was used to produce bars intended for drawing wires. The hydrostatic extrusion method was used to make bars with a diameter of 5 mm from three tested materials, while three experimental steels showed insufficient susceptibility to extrusion at high pressure and cracked at various strain values. An analysis of possible causes of bar breakage during extrusion was carried out on the basis of the results of microstructure examination.

The oxidation behavior of the CrFeCoNiAlx (x = 0, 1.0, and 5.0 wt%) high-entropy alloy synthesized with Al elemental powder via powder bed fusion technique at high temperatures

High-entropy alloys (HEAs) are promoted as promising materials for various applications, including those dealing with high-temperatures. It requires understanding of the oxidation at different temperatures, especially for such a technological process as additive manufacturing (AM), which is able to produce unique structure. The present work evaluates the oxidation resistance of the CrFeCoNiAl HEAs produced by AM of the blends of CrFeCoNi and Al powders at temperatures of 800 and 1000 ℃. Al forms the Al2O3 under the top Cr2O3 layer and prevents the delamination of the oxide scale at considered temperatures. Oxygen diffusion mainly occurs homogeneously through the columnar grain boundaries typical for AM materials. AlN precipitates under the Al2O3 formations were observed for the sample with the highest aluminium concentration due to dissolution of nitrogen in the as-built material.

Microstructure distribution and orientation-structure topology optimization of metallic materials for laser additive manufacturing

Microstructure distribution and orientation-structure topology optimization of metallic materials for laser additive manufacturing