Alternative Processing Routes Research Articles

Characterization of port dredging waste for potential used as incorporation on materials for civil construction: A case study in Brazil

Port operation activities have been expanding globally, driven by globalization and increased cargo handling. Developing countries, such as Brazil, China, and India, are experiencing a rise in the construction of modern ports. Recently, sustainability concepts have been integrated into maritime transportation, focusing on the construction and management of ports and exploring the reuse of waste generated during operations. The main objective of this study is to evaluate the potential application of the dredging material of port of açu (DMPA), sourced from a new private port in Rio de Janeiro State, Brazil, in developing sustainable construction materials. The dredged material, collected from the bottom of the shipping canal was physically, chemically, and morphologically characterized to compare its results with the processing and application requirements for alternative materials. A standard method for primary processing was developed, providing deeper insights into the material’s condition. Results indicate that the natural dredged material can be utilized as a filler in interlocking blocks or mortar. Additionally, an alternative processing route involving calcination can enhance the material's reactivity, presenting opportunities for higher-value applications, although the energy costs must be considered. The calcination of 650 °C resulted in a higher pozzolanic index, increasing its reactivity. The study concludes that port dredging waste from this case study has significant potential for use in sustainable building material development.

Severe plastic deformation of Mn-Al permanent magnets

Manganese-aluminum permanent magnets are promising candidates to fill the cost and performance gap between lower-performance bonded ferrites and high-performance magnets based on rare-earth elements. This is due to the favorable combination of saturation magnetization and magnetocrystalline anisotropy in the Mn-Al τ phase combined with low raw material cost. However, the τ phase is metastable and prone to decomposition at high temperatures, making processing by conventional milling and sintering difficult. Severe plastic deformation (SPD) is an alternative processing route to control the microstructure of a material by applying very high amounts of strain. In this study, equal-channel angular extrusion (ECAE) and high-speed high-pressure torsion (HS-HPT) were both tested as SPD processing routes. ECAE improved magnetic energy product, (BH)max, by 220% by refining the grain size and imparting a high density of dislocations. HS-HPT enabled a rapid phase transformation from the high-temperature ε phase to the τ phase but lowered Hci, making it better suited to soft magnet processing.

Extracting valuable metals from zinc sulfide concentrate: A comprehensive simulation-based life cycle assessment study of oxidative pressure leaching

Considering the increasing environmental consciousness and the imperative for sustainable development, conventional zinc smelting operations employing the roast-leaching-electrowinning process face growing environmental pressures. Consequently, the oxidative pressure leaching process has emerged as an alternative processing route. This study focuses on recovery of major metals from ZnS concentrate, building a comprehensive model to simulate the oxidative pressure leaching process. The process model built demonstrated that zinc, sulfur, indium, gallium, cadmium, cobalt, germanium, and copper could be recovered effectively, the main chemical inputs being sulfuric acid, oxygen, and lime, while zinc electrowinning constituting over 90 % of the total electricity consumption. The results were used to compile a life cycle inventory, culminating in a gate-to-gate assessment of the environmental impacts of the process. The global warming potential for the treatment of 1 t of ZnS concentrate is approximately 2,000 kg CO2 eq. The primary environmental impacts in the process are from chemical inputs and electricity consumption. Based on these findings, recommendations for sustainable production practices are proposed. These include systematic recovery and reuse of electrolytic off-gas and roasting heat, greater utilization of renewable energy, enhanced iron removal processes, and exploration of alternative chemicals for Ga and Ge recovery.

Fully Consolidated Deposits from Oxide Dispersion Strengthened and Silicon Steel Powders via Friction Surfacing

Abstract The objective of this work is to study the ability of friction surfacing to deposit metal alloys that are difficult to process with traditional methods. Creep and neutron irradiation resistant oxide dispersion strengthened (ODS) materials cannot be produced via conventional casting route due to insolubility of the oxidic and metallic alloy constituents, causing unintended inhomogeneous oxide dispersion and material behavior. Increasing silicon content of Iron-Silicon (Fe-Si) improves electromagnetic properties but embrittles the material significantly and the fusion based manufacturing methods unable to process this steel. The solid-state nature of the friction surfacing process offers a potential alternative processing route to enable wider usage of difficult to process alloy systems. Both ODS and Fe-Si materials are available in powder forms. While the existing literature in friction surfacing focuses on depositing composites by incorporating small quantities powders through holes in consumable rod, this is a first study that shows a large charge of powder can be converted to a homogeneous fully consolidated deposit in friction surfacing. A novel methodology is used that incorporates the high portion of powder feedstock into hollow consumable friction surfacing rods (up to 35% volume fraction). It was found that fully consolidated deposits can be produced with powder feedstocks using proposed methodology. A recrystallized, homogeneous, equiaxed microstructure was observed in Fe-Si 6.8 wt% and a new generation FeAlOY ODS alloy deposits processed with hollow stainless-steel friction surfacing rods. Both powder and rod material plasticize and deposit without bulk intermixing.

Alternative processing routes on CsH2PO4 proton conductors: Cold sintering and ball-milling routes

Cesium dihydrogen phosphate (CsH2PO4) holds great potential as electrolyte for intermediate-temperature fuel cells and electrochemical devices due to its high proton conductivity (≥10−2 S/cm). This study reports on the variation of the microstructure of CsH2PO4 and its effect on its electrical and thermal properties, with special attention to the low-temperature conductivity behavior. To manipulate morphology, the particle size was decreased by wet ball-milling, while variations in grain growth were achieved by cold sintering. Above the superprotonic phase transition, the electrical conductivity was effectively independent of the grain size. Nonetheless, at lower temperatures, a brick layer analysis on the impedance data revealed that the conductivity of the monoclinic phase is governed by the conduction pathways along the parallel grain boundaries due to the humidified atmosphere. Overall, we propose two conduction mechanisms that could explain the grain boundary conductivity of these samples, revealing critical links between sample morphology and low-temperature electrical behavior.

Emerging continuous SiC fibers for high-temperature applications

Silicon carbide (SiC) fibers are responsible for the ultimate strength and toughness of SiC-fiber reinforced composites in harsh environments. The development of a new generation of continuous SiC fibers continues to advance the mechanical properties of composite materials. Tyranno™ SA4 fiber was recently released as a successor of Tyranno™ SA3 fiber. Laser-driven chemical vapor deposition (LCVD) has been adopted as an alternative fiber processing route to synthesizing high-strength SiC fiber with tailorable small diameters and chemical compositions. Both Tyranno™ SA4 and laser-driven CVD fibers show very high tensile strength, about 4 GPa in the as-fabricated condition. The degradation of thermal stability and strength due to annealing in an inert environment were similar for Tyranno™ SA3 and SA4 fibers because of their similar carbon-rich, crystalline microstructure. Silicon-rich fibers produced by LCVD possessed heterogeneous crystallinity, which was attributed to laser power distribution and showed microstructural instability at 1500 °C and above. The new SiC fibers demonstrated an increase in as-fabricated strength but faced the same challenges in environmental resistance as the traditional SiC fibers do.

The effect of powder recycling on the mechanical performance of laser powder bed fused stainless steel 316L

Powder recycling refers to the reuse of unused powder feedstock in the laser powder bed fusion (PBF-LB/M) process. This approach is crucial for the economic viability and sustainability of PBF-LB/M, as powder accounts for a large proportion of the total production cost. However, through powder recycling, the physical and chemical properties of powder are liable to change. This variation in powder properties can subsequently lead to knock-on effects on the mechanical properties of a fully built component.This research has investigated the changes that occur to stainless steel 316L (SS316L) powder as a result of recycling. This includes changes to powder size distribution (PSD), flowability, chemistry and phase composition. Likewise, the impact that these changes have will also be assessed in PBF-LB/M SS316L components manufactured from powders after different levels of recycling and subjected to alternative post processing routes such as hot isostatic pressing (HIP). This comprehensive investigation involves a thorough examination of both macro- and microstructures, encompassing detailed analyses of chemical composition, microstructural features, and defects. The study aims to elucidate differences in mechanical behaviour through a series of experiments, including uniaxial tensile tests, Charpy impact assessments, and low cycle fatigue (LCF) experiments. Additionally, the investigation will be complemented by pitting potential tests, providing a holistic understanding of the material's performance and characteristics.Although moderate changes to powder were observed for both PSD and chemistry, this was found to be negligible and not enough to result in any adverse changes to part performance. In addition, the microstructure of SS316L remained stable across differing levels of powder recycling. Whereas the porosity content increased marginally as the fine particle content of powder was reduced, this was not found to be sufficient to affect the LCF performance of the material. After powder recycling, increases in ductility and Young’s modulus were attributed to a reduction in oxides present in the microstructure, which were sources of localised damage and deformation.

Characteristics of oxide-dispersion strengthened alloys produced by high-temperature severe deformation

This study is to explore an economically attractive and technically feasible processing method for oxide-nanoparticle strengthened alloys for fusion reactor application. Despite many scientific merits of the advanced oxide-dispersion strengthened (ODS) alloys, such as the nanostructured ferritic alloy (NFA) 14YWT, the only viable production path for a high-quality NFA is the high-power mechanical alloying process. This process is often a multi-day high-speed ball milling of alloy powder with a small quantity of yttria (Y2O3) powder, followed by the milled-powder consolidation using extrusion or other methods and additional thermomechanical processing (TMP) for property control. This complex production path, including the low-temperature mechanical alloying in particular, has limited technical advancement toward the cost-effective and scale-up production of ODS alloy components. To overcome such a practical limitation, we proposed to explore alternative low-cost processing routes using traditional thermomechanical processing (TMP) method only. A series of continuous TMP cycles, which were designed to impose high-temperature severe plastic deformation (HT-SPD) conditions to the consolidated powder mixtures, were applied to achieve the effective distribution of oxide particles in nanograin structure and thus desirable mechanical properties. Since the reduced-activation ferritic-martensitic (RAFM) alloy powders (Fe-10Cr and Fe-14Cr alloys with various Y contents) are available in our inventory, we focused to utilize the new solid-state synthesis approach for controlling oxide (oxygen source) dissolution and nanoscale clustering in nanograin structure in those alloys. A combination of powder consolidation at 900 °C and continuous thermomechanical activation at 600 °C yielded two essential ODS alloy microstructure contents–nanograin structure and nanoparticle distribution–and thus demonstrated a good combination of strength and ductility.

Design of Sustainable Aluminium-Based Feedstocks for Composite Extrusion Modelling (CEM).

Additive manufacturing (AM) has become one of the most promising manufacturing techniques in recent years due to the geometric design freedom that this technology offers. The main objective of this study is to explore Composite Extrusion Modelling (CEM) with aluminium as an alternative processing route for aluminium alloys. This process allows for working with pellets that are deposited directly, layer by layer. The aim of the technique is to obtain aluminium alloy samples for industrial applications with high precision, without defects, and which are processed in an environmentally friendly manner. For this purpose, an initial and preliminary study using powder injection moulding (PIM), necessary for the production of samples, has been carried out. The first challenge was the design of a sustainable aluminium-based feedstock. The powder injection moulding technique was used as a first approach to optimise the properties of the feedstock through a combination of water-soluble polymer, polyethyleneglycol (PEG), and cellulose acetate butyrate (CAB) wich produces low CO2 emissions. To do this, a microstructural characterisation was carried out and the critical solid loading and rheological properties of the feedstocks were studied. Furthermore, the debinding conditions and sintering parameters were adjusted in order to obtain samples with the required density for the following processes and with high geometrical accuracy. In the same way, the printing parameters were optimised for proper material deposition.

Double Soaking of Medium Manganese Steels

Double soaking (DS) has been proposed as an alternate processing route for medium manganese steels. DS consists of soaking in the intercritical annealing region to stimulate manganese enrichment of austenite by depletion of ferrite followed by secondary soaking at a higher temperature and cooling to room temperature to obtain a martensite/austenite microstructure. DS is different from more traditional medium manganese heat treating which usually involves a single soaking step in the intercritical region to generate a ferrite/austenite microstructure. DS has been shown effective at generating attractive tensile properties notably tensile strength levels in excess of typically observed levels in medium manganese steels. A review of properties and microstructural evolution obtained by DS of medium manganese steels is presented here.

Characterization and Comparative Study of Energy Efficient Mechanochemically Induced NASICON Sodium Solid Electrolyte Synthesis.

In recent years, there is growing interest in solid-state electrolytes due to their many promising properties, making them key to the future of battery technology. This future depends among other things on easy processing technologies for the solid electrolyte. The sodium superionic conductor (NASICON) Na3Zr2Si2PO12 is a promising sodium solid electrolyte; however, reported methods of synthesis are time and energy consuming. To this effect, attempt was made to develop a simple time efficient alternative processing route. Firstly, a comparative study between a new method and commonly reported methods was carried out to gain a clear insight into the mechanism of formation of sodium superionic conductors (NASICON). It was observed that through a careful selection of precursors, and the use of high-energy milling (HEM) the NASICON conversion process was enhanced and optimized, this reduces the processing time and required energy, and opens up a new alternative route for synthesis. The obtained solid electrolyte was stable during Na cycling vs. Na-metal at 1mA/cm2, and a room temperature conductivity of 1.8 mS/cm was attained.

Microstructural and Mechanical Analysis of Seamless Pipes Made of Superaustenitic Stainless Steel Using Cross-Roll Piercing and Elongation

The cross-roll piercing and elongation (CPE) is a forming process performed at high temperatures and high strain rates. The final product quality is strongly dependent on its microstructure. In this study, a finite element method (FEM) model was developed to better understand plastic deformation effects on microstructure during CPE and to analyze alternative thermo-mechanical processing routes. Specific models were used to simulate dynamic and meta-dynamic recrystallization (DRX and MDRX) for the processing of superaustenitic stainless steel (SASS). In addition, the CPE of SASS was investigated experimentally. The microstructure, mechanical properties, and chemical changes of the final product were assessed using optical microscopy, hardness testing, X-ray diffraction, and SEM-EDS. The results revealed higher temperatures and strain rates in the exterior area of the shell after piercing, and MDRX occurred in the whole thickness. However, an average grain size reduction of 13.9% occurred only in the shell middle and inner diameters. During elongation, the highest values of the strain rate and DRX were observed in the inner region, exhibiting a grain size reduction of 38%. Spread in terms of grain size and grain shape anisotropy was found to be less accentuated for tube samples as compared to the pierced shells.

Developing an artificial neural network controller for accelerating the hot deformation of the titanium aluminide TNM-B1 using reinforcement learning and finite element simulations

This work presents a framework for interfacing a reinforcement learning algorithm with a finite element model in order to develop an artificial neural network controller. The goal of the controller is accelerating the hot compression process of the titanium aluminide TNM-B1. The reinforcement learning algorithm interacts with the finite element model by exploring different die velocities and receiving input measurements (the velocity, displacement and force of the die) while collecting rewards if a constant stress state in the workpiece is achieved. Synthetic stochastic material behavior was used to simulate the observed variations in deformation behavior of TNM-B1. The same reinforcement learning setup and reward function was able to adapt to two example finite element environments; the compression of a simple cylinder workpiece between flat dies and the compression of a more complex bone workpiece between flat dies. The performance of the controller for the bone compression environment was comparatively reduced and less consistent. In addition, training times and training instability were significantly increased. Furthermore, the results suggest that the framework can be used as a tool to find process optimizations or alternative process routes. This work demonstrates the concept and provides the groundwork and fundamentals for transferring the method to a physical setup.

White asparagus stem proteins, from waste to interface stabilizer in food foams

White asparagus stems are a large waste stream that, despite having a high nutritional quality, is currently underutilized. Plant waste stream utilization is often based on extensive processing, which uses copious amounts of resources, and can negatively affect protein functionality. Hence, our study aimed to explore alternative processing routes and characterize the effect of asparagus extract composition on interfacial and foaming properties.Screw pressing followed by mild purification methods was used to obtain and purify protein extracts from white asparagus stems. Mild purification by filtration removed particles and purification by dialysis removed molecular impurities. Removal of particles and molecular impurities led to improved interfacial properties, as shown with drop tensiometry. The particles disturbed interfacial network formation and the presence of small impurities reduced network density and in-plane interactions. Extracts without particles and molecular impurities formed a dense interface with stiff solid-like behavior and strong in-plane interactions, which resulted in superior foam stability. Additionally, foamability was improved after filtration and/or purification, which could be related to the air bubble size and adsorption rate.In this study, we identified critical factors for interface and foam stabilizing properties of asparagus proteins, and we revealed the great potential of mildly processed asparagus stem extracts for application in food foams.

A Machinability Assessment of the Novel Application of Field-Assisted Sintering Technology to Diffusion Bond (FAST-DB) and Functionally Grade Dissimilar Nickel-Based Superalloys

This work presents an alternative processing route to the conventional powder HIP—forge route for Nickel-based superalloys. Demonstrating how the field-assisted sintering technology (FAST) process can be exploited to successfully diffusion bond or functionally grade two or more Nickel-based superalloys from powder feedstock. The robustness of the process has been further demonstrated by the successful bonding of one alloy in powder form to another in the solid form. Chemical and microstructural analysis of the diffusion bond between the alloys is characterised, in both cases, with a short diffusion zone—in agreement with thermodynamic model predictions. A gradual transition in microhardness across the bond region was measured in all samples. A machinability assessment was also carried out through a simple face turning operation. Analysis of the cutting forces and machined surface shows signs of a directionality when machining across the bond region between two alloys, indicating that care must be taken when machining multi-alloy FAST-DB components.

Avoiding Gallium Pollution in Close‐Coupled Showerhead Reactors, Alternative Process Routes

In contrast to the previous work which solved the problem of gallium pollution using hardware modifications, herein, the changes are examined to process conditions to reduce gallium pollution in InAlN layer. Using a model of GaN decomposition followed by gallium desorption and diffusion to the showerhead, different process conditions are used to limit either the desorption or the diffusion. Reducing the GaN growth temperature gives some improvement by reducing desorption, but affects channel mobility, likely due to increased carbon incorporation. Increasing the wafer–showerhead distance also reduces the gallium pollution, this time by a factor of around 2. Finally, using AlGaN layers instead of GaN as the channel completely removes gallium pollution, even for composition as low as 5%. It is suggested that in addition to reducing desorption due to alloying, the aluminum precursor may be acting as a getter for this gallium, and so stops it getting to the showerhead. A combination of these different approaches suggests that process conditions can significantly reduce gallium pollution in close‐coupled showerhead reactors.

Influence of chemical composition and processing conditions on the microstructure and magnetic properties of low-carbon Si-Al-Sb electrical steel sheets

It has been recently reported that the magnetic behavior of electrical steels containing Si + Al, can be improved by an alternative processing route, which involves the intercritical annealing of the hot-rolled bands before cold-rolling. The effects of such processing route has not been investigated in steels containing Si-Al-Sb. It has been reported that Sb can enhance the magnetic behavior of these steels. The present work reports the microstructure and magnetic properties of Si-Al-Sb electrical steels processed by the alternative processing route. Results were compared with those of Si-Al electrical steel sheets processed both by the conventional and the alternative route. Microstructural characteristics of hot-rolled electrical steel samples were modified by an intercritical annealing conducted at 850 °C from 30 min to 720 min. After this, samples were cold rolled using thickness reductions of 80 % and 90 %, and annealed at 750 °C, 850 °C and 950 °C for 8 min. Characterization of the samples included: spark optical emission spectrometry, dilatometry, optical microscopy and scanning electron microscopy, while magnetic properties were determined in a silicon steel sheet iron loss tester. Results demonstrate that, Si-Al-Sb steels processed by the alternative route exhibit better performance (higher permeability, lower coercivity, lower core loss), than Si + Al steels processed either by the conventional or the alternative route.

Micro-embossing of micro-structures in RSA-501 as mold inserts for the replication of micro-lens arrays

The production of mold inserts for the replication of micro-lens arrays through micro-embossing could be an alternative process route compared to diamond turning or milling in order to reduce time and costs. The rapidly solidified aluminum alloy RSA-501 is expected to form micro-structures with low surface roughness because of its ultra-fine grain structure. In micro-embossing challenges like elastic spring back effect, pile-ups, and forming accuracy depend on the material behavior. Therefore, RSA-501 was further characterized and the influence of polishing or flycutting on the material behavior was investigated. To further understand the grain and microstructure samples were sectioned along their cross and longitudinal directions. The grain structure of RSA-501 was oriented along the extrusion direction and the mean grain sizes were <1.00 μm. Furthermore, RSA-501 was micro-embossed to investigate the influence of the material behavior and surface preparation on the forming of micro-structures. The induced surface integrity through flycutting was not deep enough to influence the forming of micro-structures. Therefore, the workpiece surface can be prepared either by polishing or flycutting. When micro-embossing RSA-501, cross and longitudinal sections can be used. However, it is recommended to process the cross section because of its isotropic grain structure. It was shown that the curvature radius of micro-embossed concave structures differs from the tool radius. This is due to the elastic spring back effect. Since the embossed structure remains spherical, the spring back effect can be compensated by adjusting the tool radius.

Recycling‐Induced Copper Contamination of a 42CrMo4 Quench and Tempering Steel: Alterations in Transformation Behavior and Mechanical Properties

The transformation behavior and the mechanical properties of three laboratory produced steels are presented. To investigate the influence of copper contamination, the reference alloy 42CrMo4 is modified and alloyed with 0.5 and 1.0 wt% copper, respectively. The transformation behavior is investigated through dilatometry that yields continuous cooling transformation diagrams, while the mechanical properties are investigated by hardness measurements as well as Charpy‐V‐notch impact and tensile tests. Accompanying microstructure investigations by means of light optical, scanning electron, and transmissions electron microscopy and thermodynamic simulations (CALPHAD) are performed. It is demonstrated that copper contamination that will be unavoidable when increasing the overall steel recycling fraction may contain the potential for increasing the hardness as well the strength of standard high strength steels, although it is considered to be very detrimental during steel production. Together with reduced environmental footprints and production costs due to the utilization of lower grade scrap with more Cu‐contamination, the development of alternative processing routes for Cu‐contamination‐tolerant high strength steels is pursued.

A parametric study of the microstructural evolution of an advanced Ni-based superalloy powder when consolidated using Field Assisted Sintering Technology, compared to a hot isostatic pressing benchmark

The use of Field Assisted Sintering Technology (FAST) is examined for the consolidation of an advanced Ni-based superalloy powder feedstock. FAST processed material was directly compared to a benchmark material prepared via hot isostatic pressing (HIP) where it was found that density, hardness values and microstructures were comparable. FAST enables the retainment of the prior particle grain morphology when using sintering dwell times ranging from 10 to 240 min. The application of dwell temperatures above the γ′ solvus of the alloy resulted in significant grain growth. Measured densities reveal that the applied load and dwell time used during sintering have minimal effect on the final density of the consolidated material. The crystallographic texture was also shown to be isotropic in FAST consolidated material. This study demonstrates that FAST is potentially a viable complementary and/or alternative processing route for consolidating Ni-based superalloy powders.