Metal Feedstock Research Articles

Generalizable classification methodology for quantification of atomized feedstock powder by 3D X-ray tomography data and machine learning

Laser powder bed fusion (LPBF) is currently being applied to manufacture engineering-crucial components. To maintain consistent part quality, accuracy and speed in the quality assurance of atomized metal feedstock powder is critical. 3D x-ray tomography (XRT), coupled with machine learning algorithms, provides a transformative route to powder characterization and classification. A recycled AA7050 feedstock powder was studied through XRT to demonstrate a scheme for classification of highly deformed particles which vary both in geometric morphology and degree of surface irregularity. Manual, unsupervised, and supervised classification algorithms were optimized to reproduce visual classification, demonstrating how different approaches to algorithm training may provide a balance between the amount of training data and acceptable final accuracy. The reported approach provides a robust methodology that links 3D measurements and powder classification as means to control powder-induced defects and improve mechanical performance in printed parts.

Current‐Adaptive Li‐Ion Storage Mechanism in High‐Rate Conversion‐Alloying Metal Chalcogenides

AbstractBeyond the high theoretical capacity, conversion‐alloying metal chalcogenides (CAMCs) exhibit exceptional high‐rate performance as Li‐ion battery electrodes. However, the inherent origin of the high‐rate performance remains elusive, especially given the lower intrinsic conductivity of CAMCs. Here, the correlation between phase evolution and charge transport dynamics in fully activated CAMCs is systematically investigated, elucidating a current‐adaptive Li‐ion storage mechanism to explain the anomalous high‐rate performance. Briefly, the deconversion reaction manipulated by ion diffusion acts as a “regulator” to adaptively modulate the transition from metal (high electronic conductivity) and lithium chalcogenides (high ionic conductivity) to CAMCs, thus removing the charge transport bottleneck without affecting the formation of the metal feedstock required for the alloying reaction. On this basis, the high capacity can be maintained at high rates through a “fading‐free” alloying reaction. This study offers a novel perspective for the design of high‐rate electrode materials.

A study on production of hydrogen using Al scrap feedstock.

A sustainable future, concerning the energy transformation of a country, heavily relies on the availability of energy resources, particularly renewables such as solar, wind, hydropower, and clean hydrogen. Among these, hydrogen is the most promising energy source due to its high calorific value, ranging between 120 and 140MJ/kg. It has the potential to lead the market in various industries such as power generation, steel, chemical, petrochemical, and automotive. Significant research has been going on in hydrogen production technologies to reduce costs and improve competitiveness with fossil fuels. One such potential approach includes the use of metal-water reactions, which offer unique opportunities for producing clean hydrogen and other valuable byproducts. However, the quantity of hydrogen produced varies depending on the metal feedstock, type of electrolyte, and the activator or catalyst, used in combination with water. This latest work discusses recent progress on hydrogen production and the effects of variations in different parameters on the process, with a focus on aluminum (Al)-water reactions. Investigations have been conducted and reported on the effect of various activators with different concentrations, the quantity of aluminum scrap feedstock, and the volume of the electrolyte on the kinetics of the metal-water reactions and hydrogen production. Sodium hydroxide (NaOH) was observed to be more effective than potassium hydroxide (KOH) in promoting metal-water reactions. These activator-assisted metal-water reactions help produce clean hydrogen, along with other value-added products such as hydroxides. This work clearly sheds light on the potential utilization of industrial aluminum scrap as feedstock for producing clean hydrogen.

An effective approach for CH4/N2 separation using aluminum-based metal-organic frameworks (MOFs) prepared from coal fly ash

Metal-organic frameworks (MOFs) are considered one of the promising adsorbents for CH4/N2 separation. However, MOFs commercialization is a big challenge since their synthetic materials are expensive and not environmentally friendly. Herein, the dealumination solution obtained from coal fly ash (CFA) using sulfuric acid as an extracting agent through direct leaching and roasting technologies was applied as metal feedstock to prepare CFAx-FumMOF-y and compared to aluminum fumarate MOF (Al-FumMOF) in morphology, surface area, micropore volume, and CH4/N2 selective separation. The results indicated that CFAx-FumMOF-y exhibited closely similar surface area (1164.94–1073.08 m2/g) and micropore volume (0.40–0.36 cm3/g) to Al-FumMOF (1287.55 m2/g, 0.42 cm3/g), even there were no detectable differences in CH4 uptakes (CFAx-FumMOF-y, 21.93–20.69 cm3/g; Al-FumMOF, 22.13 cm3/g) at 298 K and 1.0 bar, suggesting that the impurity metal species in dealumination solution hardly affect textural properties and gas uptakes. Moreover, the isosteric heat of adsorption (Qst) and IAST CH4/N2 selectivity of CFAs-FumMOF-1 (19.25–17.84 kJ/mol) and CFAb-FumMOF-1 (18.83–18.64 kJ/mol) were slightly superior to Al-FumMOF (17.83.64–16.86 kJ/mol, 4.87), suggesting that CFAx-FumMOF-1 played an identical role as Al-FumMOF in gases separation. The cyclic regeneration experiments and binary breakthrough tests further confirmed that CFAx-FumMOF-y was feasible for practical application. This study provides a new perspective for reducing the production cost of MOFs as well as realizing high-value utilization of CFA.

7 Construction and Characterization of a Thermal Spray Coating Aerosol Generator

Abstract Thermal spray coating (TSC) is a surface treatment process whereby feedstock material is sprayed onto surfaces under pressure where it solidifies and forms a solid coating. In metal TSC processes, large quantities of aerosols, including fine and ultrafine metal particles are generated. However, exposure assessment for TSC is lacking. The goal of this study was to construct a TSC aerosol generation system and to characterize the physicochemical properties of aerosols generated during coating processes. A computer-controlled, automated electric arc wire-TSC aerosol generator system was built in an enclosed room, where a rotary motor rotates a metal feedstock pipe in circular and up-and-down directions to allow even deposition of coating material on the pipe surface. The characteristics of aerosolized particles during spray coating using a stainless-steel wire (PMET 720) showed that: 1) respirable mass concentrations ranged from 142–218 mg/m3 (3 spray shots with each shot of 1-sec during 20-min sampling), 2) diameter of peak particle number concentrations was between 360 nm and 400 nm, 3) mass median aerodynamic diameter determined by an impactor ranged from 290–370 nm, 4) particle morphology was observed to be diverse including chain-like agglomerates and spherical and cylinder-like shapes, and 5) metal composition was 80% iron, 17% chromium, and 3% manganese with trace amounts of nickel and copper. These findings are limited to one wire type and suggests the need for further investigations evaluating various parameters (e.g., wire/powder types, high/low energy, ventilation on/off) to obtain emission rates and recommend control measures.

3D printing of fine-grained aluminum alloys through extrusion-based additive manufacturing: Microstructure and property characterization

• A new extrusion-based solid-state metal additive manufacturing method was developed. • The new method enables direct deposition of fine-grained aluminum alloy without melting. • The new method uses off-the-shelf metal rods rather than pricy powders as feedstock. • The printing process was completed in an open-air environment, avoiding costly inert or vacuum conditions. • The printed 6061 aluminum alloys yield the strength and ductility comparable to wrought 6061 aluminum alloys. Additive manufacturing (AM) has the potential to transform manufacturing by enabling previously unthinkable products, digital inventory and delivery, and distributed manufacturing. Here we presented an extrusion-based metal AM method (refer to “SoftTouch” deposition in the filed patent) that is suitable for making the metal feedstock flowable prior to the deposition through dynamic recrystallization induced grain refinement at elevated temperatures. The flowable metal was extruded out of the printer head like a paste for building dense metal parts with fine equiaxed grains and wrought mechanical properties. Off-the-shelf metal rods were used as feedstock and the printing process was completed in an open-air environment, avoiding pricy powders and costly inert or vacuum conditions. The resulting multi-layer deposited 6061 aluminum alloys yield the strength and ductility comparable to wrought 6061 aluminum alloys after the same T6 heat treatment. The extrusion-based metal AM method can also be advanced as green manufacturing technologies for fabricating novel alloys and composites, adding novel features to existing parts, repairing damaged metal parts, and welding advanced metals for supporting sustainable manufacturing, in addition to being developed into a cost-effective manufacturing process for the fabrication of dense metal of complex structural forms.

Evaluation of the infill design on the tensile properties of metal parts produced by fused filament fabrication

Additive Manufacturing (AM) applications have expanded significantly from rapid prototyping to high-end products such as complex spare parts. AM has enabled advantages of reduced material usage, geometric freedom, and production automation, shaping the future of the manufacturing industries. With the rapid expansion of AM applications, feedstock materials have developed noticeably, from polymers and ceramics to metals and composites. The progress in metal feedstock material discoveries has empowered the exploration of implementing new AM technologies. Fused Filament Fabrication (FFF) is one of the most common and cost-effective material extrusion AM technologies. This study explores the effect of the infill pattern on the tensile mechanical properties of metal parts produced via FFF, using two feedstock materials, 17-PH stainless steel and copper. Two approaches are designed to investigate the results: experimental tensile test, and Finite Element Analysis (FEA) with digital twin reconstruction method. Results show that 17-4 PH Stainless Steel samples with a triangular infill exhibited a 42% drop in ultimate tensile strength compared to solid infill. However, it also revealed a 34% reduction in mass, cost saving of 36%, and a faster fabrication with a 25% reduction in lead time. At the same time, copper samples with triangular infill exhibited a 22% drop in ultimate tensile strength and a 12% mass reduction. However, it revealed a similar lead time with only a 3% reduction. A Scanning Electron Microscope (SEM) was used to investigate the parts’ internal structure and average pore size, to understand the failure mode of the test specimens.

Measurement and analysis of impact dynamics suitable for modelling pneumatic transport of metallic powder flow through a directed energy deposition nozzle

In blown powder directed energy deposition (DED) additive manufacturing powdered metal feedstock is pneumatically conveyed to the meltpool via a nozzle. DED nozzles have been the subject to a growing number of research efforts using computational fluid dynamics (CFD) with multiphase flows to study and optimize powder flow. However, many research papers published to date contain powder – nozzle impact dynamics behavior that is not realistic or not derived from experiments that resemble the powder conveyance process in the DED nozzle being studied. To provide a set of data representative of DED powder flow through a nozzle particle image velocimetry (PIV) experiments were conducted using 316L stainless steel metal powder and flat targets with varying surface roughness made of oxygen free copper, mild steel, P20 tool steel, 316L stainless steel, Inconel 718, and Ti-Al6-V4. Normal coefficients of restitution (COR) were calculated and compared to several analytical and empirical models in literature.

A new solution for assessing the printability of 17-4 PH gyroids produced via extrusion-based metal AM

Robust assessments of printability limits in complex geometries represents a key point for enabling the adoption and the spreading in industry of innovative Additive Manufacturing (AM) technologies.The paper presents a novel solution to assess a printability map in metal AM able to capture the probability of producing a defect-free complex geometries embedding all the printing constraints and the geometrical specifications. The approach involves logistic regression as tool to assess the likelihood of obtaining defect-free complex geometries, depending on the process and the material at hands.Besides proposing a new methodology which can be adopted for any printed geometry, the paper investigates the printing capability of a new emerging AM technologies based on extrusion of metal feedstock, such as the Bound Metal Deposition from Desktop Metal, for defect-free fabrication of an emerging lattice-based shape, known as Schoen gyroid.The proposed method is based on combining quality data labeled by experts with failure mode analysis of the 3D printing process within a logistic regression model. The approach provides a final probabilistic map, in the design parameters space of the gyroids, where the likelihood of defectiveness is available at each location of the design space. The proposed methodology and the presented results support the development of robust defect- and waste-free part design approaches for AM.

Understanding Flow Characteristics in Metal Additive Manufacturing

In fluid flow, the frictional effects from interior surfaces of flow components create pressure loss across the surface. Understanding this inherent pressure loss due to friction and other phenomena is important when designing a flow system. For conventional manufacturing, friction loss has been empirically studied and is well known in the engineering community. However, newer manufacturing techniques, such as laser powder bed fusion (LPBF), an additive manufacturing technique, need to be understood. The inherent flow conditions resulting from the additive processes were studied. Test samples were printed with the flow path oriented in the vertical direction with different channel diameters to characterize the inherent fundamental flow properties of the process. Moody diagrams were replicated for a greater understanding of possibilities and shortfalls when implementing LPBF into design applications. Experimental flow testing revealed that greater effective sand grain roughness resulted from this process when compared to conventional machining methods. This roughness did not correlate well to the average roughness measured with a laser scanning microscope but was consistent with the average particle size of the powder metal feedstock.

Evolution of the \u03b5 and \u03b3 phases in biodegradable Fe\u2013Mn alloys produced using laser powder-bed fusion

The key feature of Fe–Mn alloys is gradual degradability and non-magneticity, with laser power bed fusion (LPBF) parameters influencing the microstructure and chemical composition. Our study focuses on biodegradable Fe–Mn alloys produced by mechanically mixing pure metal feedstock powders as part of the LPBF process. The Mn content and, consequently, the γ-ε phase formation in LPBF samples are directly correlated with an adapted energy–density (E) equation by combining the five primary LPBF parameters. We varied laser power (P) in a range of 200–350 W and scanning speed at 400 and 800 mm/s, and a comprehensive study was performed on samples with similar E. The study also showed an almost linear correlation between the LPBF's laser power and the material's hardness and porosity. The corrosion resistance was significantly reduced (from 13 to 400 μm/year) for the LPBF samples compared to a conventionally produced sample due to the dual-phase microstructure, increased porosity and other defects. The static immersion test showed that the process parameters greatly influence the quantity of oxides and the distribution of their diameters in the LPBF samples and, therefore, their corrosion stability. The most challenging part of the study was reducing the amount of ε phase relative to γ phase to increase the non-magnetic properties of the LPBF samples.

Preparation of coal fly ash derived metal organic frameworks and their carbon derivatives

In this study, a new strategy for preparing metal organic frameworks (MOFs) using coal fly ash (CFA) as a metal feedstock is introduced. Aluminium and other metal species were leached out from CFA using sulfuric acid and reacted with fumaric acid following a procedure that had been optimized to mimic Aluminium fumarate MOF (Al-FumMOF). Despite the presence of different metals in the synthesis solution, the prepared coal fly ash derived MOF (CFA-FumMOF) exhibited almost similar characteristics to Al-FumMOF synthesized using commercial chemicals. In this case, the surface area of 1236 m2/g was obtained for CFA-FumMOF, whereas that of Al-FumMOF was 1266 m2/g. For pore enhancement, the prepared CFA-FumMOF was subjected to direct carbonization and resulted in improved surface area (i.e. increase from 1236 m2/g to 2017 m2/g). The developed innovative strategy of using CFA leachate in MOF synthesis has the potential for lowering the cost of producing MOFs as well as create a new route for value-addition of the waste CFA for many applications.

A simple route for additive manufacturing of 316L stainless steel via Fused Filament Fabrication

• Feedstock made of 65 % volume fraction 361L stainless steel with 35 % LDPE was developed. • 3D printing of metal feedstock was carried out by fused filament fabrication (FFF). • 3D printed parts were thermally debound and sintered into 91–93% densified steel parts. The low-cost material extrusion (MEX) additive manufacturing technology can offer an economical alternative to manufacture metal parts with complex geometry over traditional manufacturing or the more expensive powder bed fusion (PBF) techniques. In this work, a feedstock made of 316L stainless steel powder (65 % by volume) and a single component binder (LDPE) system was developed. The use of a single binder rather than two or more components, commonly used in metal MEX, introduces a novel and more sustainable solution in terms of costs and less use of chemicals. The rheology and processability of the feedstocks were studied, and samples were 3D printed. Debinding and sintering under a hydrogen atmosphere at 1380 °C were performed, and the resulting metallic parts have been characterized by a mechanical and microstructural point of view. The results show a sintered steel having 93 % of the theoretical density and an austenitic phase confirming that the post-processing under reductive atmosphere protected the samples from oxidation and other contamination. The sintered 3D parts show a grain size of ∼ 45 μm, a yield point of 250 MPa, a tensile strength of 520 MPa, and a Vickers microhardness of 285 HV typical of annealed steel.

Effects of Direct Thermal Method Processing Parameters on Mechanical Properties of Semisolid A6061 Feedstock

This paper highlights the effects of pouring temperature and holding time on the mechanical properties of aluminium 6061 semisolid feedstock billets. The semisolid metal feedstock billets were prepared by a direct thermal method (DTM), in which the molten metal was poured into a cylindrical copper mould with a different combination of pouring temperature and holding time before it was solidified in room temperature water. The results show that the sample with pouring temperature slightly above aluminium 6061 liquidus temperature has the lowest porosity, thereby the highest mechanical properties value. The sample with a pouring temperature of 660 °C and holding time of 60 s has the density, tensile strength and hardness properties of 2.701 g/cm3, 146.797 MPa, and 86.5 HV, respectively. Meanwhile, the sample at a pouring temperature of 640 °C and holding time of 20 s has density, tensile strength and hardness properties of 2.527 g/cm3, 65.39 MPa, and 71.79 HV, respectively. The density and fractography tests were conducted to confirm the existence of porosity within the samples. The results from these experimental works suggested that the mechanical properties of DTM semisolid feedstock billet merely depended on processing parameters, which influenced the porosity level within the feedstock billet, thus directly affected their mechanical properties.

Microplasma Synthesis of Metal Feedstock for Additive Manufacturing

By expanding the boundaries of microplasma synthesis of metal feedstock beyond noble metals, this work shows that microplasmas are an excellent tool for the synthesis of a variety of transition metals and alloys. With this expansion into various alloys, microplasma synthesis can become a useful fabrication technique for producing metal feedstock for additive manufacturing due to the traditional methods being energy inefficient processes. In this work, we present results on microparticle formation of select transition metals, bimetallic alloys, such as Invar, and both austenitic and ferritic stainless steel produced through an atmospheric microplasma synthesis with a liquid electrode. We explore the production rates under different plasma parameters and at different electrolytic concentrations to help ensure efficient production of metal feedstock microparticles. During processing, the microplasma was monitored with a Langmuir probe; this assisted in determining that an aqueous solution of cobalt ions provided the best results for stainless-steel particle formation due to their higher kinetic energy in the plasma. With the ability to not only produce elemental transition metal microparticles but also complex metal alloys, such as stainless steel, microplasma synthesis, due to its energy efficiency, is ideal for creating metal feedstock for additive manufacturing.

Manganese-Based Metal Organic Framework from Spent Li-Ion Batteries and its Electrochemical Performance as Anode Material in Li-ion Battery

Herein, we report a method of recycling spent lithium-ion batteries (LIBs) cathode materials by utilizing them as a metal feedstock for the synthesis of Mn-based metal-organic frameworks (Mn-MOF). Spent cathodes were converted to manganese salts using acids (HCl and H2SO4) and reacted with commercial benzene-1,4-dicarboxylic acid (H2BDC), as an organic linker. The LIB-derived metal salts were compared to commercial available MnCl2 salt in the formation of Mn-MOFs. Mn-MOFs from spent LIBs (MOF(Cl2) and Mn-MOF(SO4)) exhibited similar morphological, structural and textural properties when compared to that obtained from commercial MnCl2 salt. HCl obtained MOF (Mn-MOF(Cl2)) was analysed for electrochemical properties due to its superior structural properties. It achieved coulombic efficiency of approximately 99% and discharge capacity of 1355 mAh g−1 as compared to Mn-MOF obtained using commercial salt (Mn-MOF(Com)) with a discharge capacity of 772.55 mAh g−1 at 100 cycles. The developed LIBs recycling strategy has the potential for contributing to existing LIBs recycling strategies and as well to the circular economy.

Increase of capacity in electric arc-furnace steel mill factories by means of a demand-side management strategy and ampacity techniques

An electric arc-furnace is a complex industry which demands high levels of electrical energy in order to heat iron materials and other additives needed for the production of cast iron and/or steelmaking. The cost of the electrical energy demanded by the factory during the production can be greater than 20% of the overall cost. This kind of arc-furnace allows the production of steel with levels of scrap metal feedstock up to 100%. From an electrical point of view, the factory size in terms of its maximum apparent power demanded from the grid is designed to make use of the static capacity of the transmission line that supplies the energy. In that case, it is not possible to increase the power of the factory above the static rating by adding new facilites without installing new transmission infrastructures. This paper presents a methodology that allows an increase in net power of an arc-furnace factory without installing new transmission lines. The novelty of the proposed solution is based on a mix strategy that combines Demand-Side Management (DSM) methodologies and the use of ampacity techniques according IEEE 738 and CIGRE TB601.The application of DSM methodologies provides an improvement in the sustainability of not only the industrial customer but also in the overall grid. As a secondary effect, it reduces operational costs and the greenhouse gas emissions.The proposed methodology has been tested in an arc-furnace factory located in the North of Spain.

Development and Characterization of Injection Moulding Mould for Ulna Implant

Metal injection moulding is a method by which metal parts are produced near net form by using metal feedstock. Current medical implants are products that must meet rigorous material, technology and functionality specifications. Corrosion resistance, bio-compatibility, bio-adhesion, bio-functionality and accessibility are the main medical desires of all medical implants. This work focused on the design and production of ulna plate implants using metal injection moulding. To be details on this, maximum stress and shrinkage of ulna implant components are studied. The size after demoulded from cavity was measured and compare to the cavity size. The range of shrinkage is observed by weights lost after debinding process that the result shows 0.1 gram decreased. The average maximum stress is 5.2749 MPa. Based on the result, the products are brittle after debinding process.

Towards a circular metal additive manufacturing through recycling of materials: A mini review

Additive manufacturing is a new emerging technology which is ideal for low-to-zero waste production, and it is considered to be a green and clean process that has the potential to lower the cost and energy consumption of production. However, the cost of the feedstock for additive manufacturing and the additive manufactured parts is usually very high, which hinders the further application of additive manufacturing, especially for the metal additive manufacturing. The concept of circular metal additive manufacturing involves the recycling of the metal feedstock and the additive manufactured parts leading to the truly zero waste production and the most energy saving. This paper reviews the technologies that help the formation of a circular metal additive manufacturing through recycling of the feedstocks and the damaged metal parts. Reactive metals, such as titanium, tend to be contaminated easily during handling and production. Recycling of the titanium for achieving a circular titanium additive manufacturing is reviewed in detail.

Probing Ultrafast Dynamics in Laser Powder Bed Fusion Using High-Speed X-Ray Imaging: A Review of Research at the Advanced Photon Source

Additive manufacturing (AM) is a transformative technology that opens up many exciting opportunities. In metal AM processes, high-power heat sources are often used to locally fuse the metal feedstock to the previous layer. Extreme thermal conditions are involved and unique microstructures are developed in AM-processed materials. At the Advanced Photon Source, we applied high-speed x-ray imaging to probe the ultrafast dynamics of the vapor depression, melt flow and particle spattering, among other transient phenomena. Demonstrated by the scientific cases reviewed and cited here, high-speed x-ray imaging is a unique tool for metal AM research. It provides invaluable information that can help address the critical issues in AM associated with structural defects, high-fidelity models, build reliability and repeatability.