Atomized Powders Research Articles

Particle size dependence of the microsegregation and microstructure in the atomized Ni-based superalloy powders: Theoretical and experimental study

The microstructure and microsegregation of atomized powder, which depend on their sizes, are of great importance to the mechanical properties of the consolidated bulk materials. Therefore, it is necessary to reveal the relationship between particle size and powder attributes. The effects of particle size on the solidification characterization of the atomized Ni-based superalloy powders were studied via finite element simulation. Based on the simulations, a model was developed to predict the microsegregation and microstructure of atomized powders with different sizes and study the influence of thermal history on the powder attributes during the atomization processes. The radiation heat transfer and temperature gradient within the rapid solidification alloy powders were taken into account in this model. For validating the accuracy of the model, the predictions of the present model were compared with the microsegregation and microstructure of the specific size powder close to the screen mesh size. The results showed that microstructure depended primarily on the temperature gradient within the powder, while the solidification rate had a more significant effect on the microsegregation. The model predicted microstructure features in agreement with the experiment, and for microsegregation, the deviations of prediction for most elements were less than 10%. This work provides a new model to precisely predict the microsegregation and microstructure of the atomized alloy powders and sets a foundation to control the powder features for various engineering applications.

Additive manufacturing of Al18Co30Cr10Fe10Ni32 high entropy alloy by gas atomization and laser powder bed fusion

Dense and crack-free, novel, eutectic Al18Co30Cr10Fe10Ni32 high entropy alloy was additively fabricated by the laser powder bed fusion (LPBF) using gas atomized alloy powders. LPBF parametric optimization was performed as a function of laser power (200–350 W) and scan speed (300–1800 mm/s). Microstructure of the densest sample exhibited a unique trimodal microstructure, along the build direction, consisting of fine cellular, coarse cellular, and conventional lamellar eutectic structures of face centered cubic (FCC) and body centered cubic (BCC) phases. This microstructural variation was significantly different from the starting powder microstructure, and the melt-pool microstructure observed during single laser scanning of arc-melted bulk alloy. The as-built alloy exhibited the outstanding tensile properties of yield strength, σY = 1.06 GPa, tensile strength, σUTS = 1.37 GPa, and elongation at failure, El = 21.3%.

Comparative assessment of gas and water atomized powders for additive manufacturing of 316 L stainless steel: Microstructure, mechanical properties, and corrosion resistance

In this study, the microstructure, and mechanical properties of 316 L stainless steel (SS316L) produced by laser powder bed fusion (LPBF) using water-atomized (WA) and gas-atomized (GA) powders were compared. The results showed that the use of WA powder, with a finer average particle size and better spreadability, led to significantly higher values of tensile strength (UTS), yield strength (YS), elongation (El%), and toughness in the WA samples (728 MPa, 580 MPa, 31.8%, and 215 J/m3, respectively) compared to the GA sample (602 MPa, 503 MPa, 25.2%, 145 J/m3, respectively). The WA samples also exhibited a non-uniform hardness distribution and superior work-hardening rate due to the presence of multiple inclusions that tightly bound to the matrix and created stress fields, increasing the required energy for dislocation motion. The higher solidification rate of melt pools in the WA sample left more intensive residual stress with distorted grains, exhibiting a higher grain orientation spread (GOS). Additionally, a multitude of geometrically necessary dislocations (GNDs) formed around the boundaries of elongated grains with tilted boundaries to maintain lattice continuity, resulting in a higher kernel average misorientation (KAM) and congestion of low-angle grain boundaries (LAGBs), particularly in the WA sample. XRD patterns confirmed the higher lattice distortion in the WA sample, and the smaller cellular structures observed in SEM images were consistent with the higher dislocation density observed in the WA specimens. Finally, the WA sample exhibited lower surface roughness and rather higher resistance to corrosive media containing chlorides.

Effects of essential oil-based formulation on biopesticide activity

Essential oils (EOs) represent a promising source of biopesticides, given their compositional complexity which bestows them high insect specificity and low risk of inducing resistance. However, their use in agriculture remains limited by their rapid degradation, limited duration of effect and non-target toxicity. These issues largely result from the under-optimized methods currently used to formulate EOs, in which their volatile organic compounds (VOCs) are poorly protected. In this study we compared pure Artemisia and Rosemary EOs to EOs formulated in three, low-cost, relatively simple, and easily applicable manners: as nanoemulsions, atomized powders, and Natural Deep Eutectic Solvents (NaDES). 24 hours after formulation, the entomotoxicity and phytotoxicity of the EOs were tested on Bemisia tabaci infested tomato plants. The identity and relative abundance of VOCs present in all formulations were also assessed 24 hours post-preparation using GC-MS and GC-FID. Nanoemulsions proved the most entomotoxic of formulations, followed by NaDES and pure EOs, while atomized powders were not significantly more entomotoxic than the control. Entomotoxicity was coupled with phytotoxicity for all formulations, except NaDES which induced particularly high rates of B. tabaci mortality when prepared with Rosemary EO, in addition to reducing damages on treated plants. Total VOC abundance depended on VOC release kinetics, determined by formulation, which although higher for pure EOs, was more gradual for NaDES. These results show the importance of EO formulation and the potential for NaDES to provide effective, sustained pest control.

Phase formation behavior and hydrogen sorption characteristics of TiFe0.8Mn0.2 powders prepared by gas atomization

In this article we have investigated the phase formation behavior and hydrogen storage characteristics of TiFe0.8Mn0.2 samples produced by electrode induction melting gas atomization (EIGA) as well as conventional vacuum arc-melting (VAM). TiFe (46Ti–46Fe–8Mn (wt%) with cubic, CsCl-type structure) and C14 Laves (37Ti–51Fe–12Mn (wt%) with hexagonal, MgZn2-type structure) phases were detected in both atomized powders and crushed ingots, the latter possessing a lower fraction of Laves phase. Microstructural characterization included electron probe micro-analysis (EPMA) and transmission electron microscopy (TEM), which evidenced the existence of a non-equilibrium Ti2Fe phase in the atomized powders. The formation of this additional secondary phase was attributed to the rapid cooling rate during powder manufacturing, based on earlier findings and phase formation thermodynamic calculations combined with Scheil solidification simulations. In addition, kinetics and pressure-composition isotherms (PCIs) were acquired to determine both absorption and desorption enthalpy/entropy, as well as to study the influence of the synthesis route (and hence the resulting microstructure) on kinetics, thermodynamics and reaction mechanisms of the TiFe0.8Mn0.2 alloy.

Assessment of Ferritic ODS Steels Obtained by Laser Additive Manufacturing

This study aims to assess the potential of Laser Additive Manufacturing (LAM) for the elaboration of Ferritic/Martensitic ODS steels. These materials are usually manufactured by mechanical alloying of powders followed by hot consolidation in a solid state. Two Fe-14Cr-1W ODS powders are considered for this study. The first powder was obtained by mechanical alloying, and the second was through soft mixing of an atomized Fe-14Cr steel powder with yttria nanoparticles. They are representative of the different types of powders that can be used for LAM. The results obtained with the Laser Powder Bed Fusion (LPBF) process are compared to a non-ODS powder and to a conventional ODS material obtained by Hot Isostatic Pressing (HIP). The microstructural and mechanical characterizations show that it is possible to obtain nano-oxides in the material, but their density remains low compared to HIP ODS steels, regardless of the initial powders considered. The ODS obtained by LAM have mechanical properties which remain modest compared to conventional ODS. The current study demonstrated that it is very difficult to obtain F/M ODS grades with the expected characteristics by using LAM processes. Indeed, even if significant progress has been made, the powder melting stage strongly limits, for the moment, the possibility of obtaining fine and dense precipitation of nano-oxides in these steels.

Precipitate Size in GRCop-42 and GRCop-84 Cu-Cr-Nb Alloy Gas Atomized Powder and L-PBF Additive Manufactured Material

Laser powder bed fusion (L-PBF) of Glenn Research Copper 42 or 84 (GRCop-42 or GRCop-84) produces a Cr2Nb precipitation-hardened high-conductivity copper alloy with tensile strength superior to other competing copper alloys. Precipitate diameters within GRCop-42 gas-atomized powder increase with powder diameter due to slower cooling rates, however, unlike GRCop-84, no threshold diameter above which extensive precipitate agglomerations form was observed in GRCop-42. Large Cr2Nb crystals were observed in GRCop-42 powder particles, implying formation within the crucible melt. A consistent precipitate volume of ~7% over a range of powder particle diameters indicated a consistent atomization process. Occasional voids were observed in GRCop-42 powder. Precipitate size was refined in L-PBF GRCop-42 to a greater extent than in GRCop-84, improving Orowan strengthening, however, this benefit was lost after heat treatment due to greater coarsening of precipitates. Precipitates in GRCop-42 accumulated on grain boundaries during heat treatment to a greater extent than in GRCop-84.

Enhanced mechanical properties by laser powder bed fusion using cost-effective hydride-dehydride titanium powders

The high cost of powder feedstock has emerged as a critical issue in additive manufacturing of titanium (Ti). In this work, pure Ti parts were successfully produced via laser powder bed fusion (LPBF) by employing cost-effective hydride-dehydride (HDH) powders modified through gas-soild fluidization. The microstructures and tensile properties were comprehensively investigated as a function of scanning speed. The pure Ti parts made under the optimized processing parameter exhibited an ultimate tensile strength of 826.1 MPa with a fracture strain of 22.3% at room temperature, superior to those made by the expensive atomized powders. The fatigue performance of the LPBF-made pure Ti using the HDH powders is comparable to those made by rolling. The excellent mechanical performance can be attributed to the effects of grain refining, texture evolution, dislocation recovery, and cyclic softening by dislocation cells and tangles generated. This work provides an effectively low-cost route to fabricate pure Ti by LPBF with excellent mechanical properties, which also serves as a useful guidance on the processing window setup using the HDH powder.

Gas Atomization of Duplex Stainless Steel Powder for Laser Powder Bed Fusion.

Duplex stainless steel powders for laser additive manufacturing have not been developed extensively. In this study, the melts of a super duplex stainless steel X2CrNiMoCuWN25-7-4 (AISI F55, 1.4501) were atomized with different process gases (Ar or N2) at different atomization gas temperatures. The process gas N2 in the melting chamber leads to a higher nitrogen dissolution in the steel and a higher nitrogen content of the atomized powders. The argon-atomized powders have more gas porosity inside the particles than the nitrogen-atomized powders. In addition, the higher the atomization gas temperature, the finer the powder particles. The duplex stainless steel powders showed good processability during PBF-LB/M (Laser powder bed fusion). The gas entrapment in the powder particles, regardless of the gas chemistry and the gas content, appears to have a negligible effect on the porosity of the as-built parts.

Effect of Hot Isostatic Pressing of Water Atomized AISI 316L Manufactured by Laser Powder Bed Fusion

The objective of this work is to study the possibility of obtaining dense parts using water atomized AISI 316L steel powder in the L-PBF process. Despite its irregular, non-spherical, particle morphology, it has a significantly lower cost. 25 samples were produced varying the laser power and the scanning speeds to determine the optimal processing conditions. Additionally, hot isostatic pressing (HIP) was performed after the L-PBF process to further increase densification. Selected samples were subjected to microstructural characterization. The best densification results obtained were for the sample produced with the laser power of 173 W and scanning speed of 600 mm/s, where densifications close to 98% were obtained. HIP post-processing promoted increased densification of samples with closed porosity, allowing samples with densification above 95% to reach values close to 100%. HIP did not promote the closure of open pores. The results indicate that the use of water atomized AISI 316L in the L-PBF process combined with post-processing by HIP can produce dense engineering components and at the same time reduce the production costs of the manufactured components, mainly because it is a lower cost raw material when compared to the commonly used feedstock obtained by gas atomization.

Spray-Dried Inhalable Powder Formulations of Gentamicin Designed for Pneumonic Plague Therapy in a Mouse Model.

Infection with Yersinia pestis (Y. pestis) may cause pneumonic plague, which is inevitably fatal without treatment. Gentamicin (GM), an aminoglycoside antibiotic, is a drug commonly used in the treatment of plague. However, it requires repeated intramuscular or intravenous administration. Pulmonary drug delivery is noninvasive, with the advantages of local targeting and reduced risk of systemic toxicity. In this study, GM powders were prepared using spray-drying technology. The powders displayed good physical and chemical properties and met the requirements for human pulmonary inhalation. The formulation of the powders was optimized using a 32 full factorial design. A formulation of 15% (w/w) of L-leucine was prepared, and the spray-drying process parameters using an inlet temperature of 120°C and a 15% pump rate were determined to produce the best powder. In addition, the optimized GM spray-dried powders were characterized in terms of morphology, crystallinity, powder fluidity, and aerodynamic particle size distribution analysis. In a mouse model of pneumonic plague, we compared the therapeutic effects among three administration routes, including subcutaneous injection, liquid atomization, and dry powder atomization. In conclusion, our data suggest that inhalation therapy with GM spray-dried powders is an effective treatment for pneumonic plague.

THERMOPHYSICAL CHARACTERISTICS OF THE HVAF COATING FROM QUASICRYSTALLINE ALLOY OF THE Al-Cu-Fe SYSTEM

The article deals with the results of determining the thermal conductivity coefficient from quasicrystalline coatings of the Al-Cu-Fe system in the temperature range up to 900 °C. The Al-Cu-Fe quasicrystalline alloy acquires a great interest for practical use as a material for protective coatings. The Al-Cu-Fe alloy is used to produce thermal barrier coatings in internal combustion engines, non-stick coatings on chemical synthesis equipment and in the food industry and to prevent the icing in aviation. The Al-Cu-Fe quasicrystals have low density, high hardness, high elasticity modulus, high values of corrosion resistance and wear resistance, low coefficient of friction, lowered adhesion, low thermal conductivity in combination with the coefficient of thermal expansion, which is close by its value to some metals. The water atomized Al63Cu25Fe12 powder with a dispersion of +40/-63 μm that has a content of the quasicrystalline phase of about 60 wt. % was used for spraying. The coating was sprayed to the butt of a cylindrical substrate from steel 45 (diameter – 25 mm, height – 10 mm), which before spraying was subjected to jet-abrasive treatment by corundum powder with a determining particle size of 1 mm at air pressure of spraying of 0.5 MPa. The Al-Cu-Fe coating with a thickness of more than 0.8 mm was made by high-speed air-fuel (HVAF) spraying using a burner GVO-RV12 with the following spraying mode: the pressure in the combustion chamber of the burner is 1.0 MPa; the oxidant excess coefficient a ≈ 1.2, the spraying distance is 270 mm. The samples were installed on the side surface of the drum (diameter 120 mm), which rotates at a speed of 2.0 rev/s (the speed of movement of the sputtering spot is 0.8 m/s). Spraying was done in three steps of 10 seconds each with a 30 second cooling time between them. Determination of the temperature dependence of the thermal conductivity of the coating was carried out by solving the inverse problem of thermal conductivity by one-dimensional temperature fields in samples obtained by single-sided jet heating with an industrial hot air torch (at surface temperatures up to 450 °C) and an oxygen-propane welding torch (at temperatures above 450 °C). It is shown that the values of the thermal conductivity coefficient of Al-Cu-Fe quasicrystalline coatings in the range of 20 °С…900 °С vary within λ = 1.9 – 2.31 W/(m×K).

THERMOPHYSICAL CHARACTERISTICS OF THE HVAF COATING FROM QUASICRYSTALLINE ALLOY OF THE Al-Cu-Fe SYSTEM

The article deals with the results of determining the thermal conductivity coefficient from quasicrystalline coatings of the Al-Cu-Fe system in the temperature range up to 900 °C. The Al-Cu-Fe quasicrystalline alloy acquires a great interest for practical use as a material for protective coatings. The Al-Cu-Fe alloy is used to produce thermal barrier coatings in internal combustion engines, non-stick coatings on chemical synthesis equipment and in the food industry and to prevent the icing in aviation. The Al-Cu-Fe quasicrystals have low density, high hardness, high elasticity modulus, high values of corrosion resistance and wear resistance, low coefficient of friction, lowered adhesion, low thermal conductivity in combination with the coefficient of thermal expansion, which is close by its value to some metals. The water atomized Al63Cu25Fe12 powder with a dispersion of +40/-63 μm that has a content of the quasicrystalline phase of about 60 wt. % was used for spraying. The coating was sprayed to the butt of a cylindrical substrate from steel 45 (diameter – 25 mm, height – 10 mm), which before spraying was subjected to jet-abrasive treatment by corundum powder with a determining particle size of 1 mm at air pressure of spraying of 0.5 MPa. The Al-Cu-Fe coating with a thickness of more than 0.8 mm was made by high-speed air-fuel (HVAF) spraying using a burner GVO-RV12 with the following spraying mode: the pressure in the combustion chamber of the burner is 1.0 MPa; the oxidant excess coefficient a ≈ 1.2, the spraying distance is 270 mm. The samples were installed on the side surface of the drum (diameter 120 mm), which rotates at a speed of 2.0 rev/s (the speed of movement of the sputtering spot is 0.8 m/s). Spraying was done in three steps of 10 seconds each with a 30 second cooling time between them. Determination of the temperature dependence of the thermal conductivity of the coating was carried out by solving the inverse problem of thermal conductivity by one-dimensional temperature fields in samples obtained by single-sided jet heating with an industrial hot air torch (at surface temperatures up to 450 °C) and an oxygen-propane welding torch (at temperatures above 450 °C). It is shown that the values of the thermal conductivity coefficient of Al-Cu-Fe quasicrystalline coatings in the range of 20 °С…900 °С vary within λ = 1.9 – 2.31 W/(m×K).

Microstructural characterization of atomized U3Si2 powders with different silicon contents (7.4–7.8 wt%)

Atomization processes are used to produce uranium-based powders for the manufacturing of dispersion fuel for nuclear research reactors. Whereas this process is considered worldwide as a reference for U-Mo powder production, its use for U3Si2 is still limited.In this paper, the microstructure of as-atomized nearly stoichiometric (7.4 wt% Si) and hyper-stoichiometric (7.6 and 7.8 wt% Si) U3Si2 powders is studied in detail. A wide range of analytical techniques were applied: X-ray diffraction (XRD), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), electron backscattered diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS) at both micrometer (SEM) and nanometer (STEM) scales. These analyzes lead to an original description of the microstructure of these as-atomized U3Si2 particles.It is shown that most of atomized particles contain only a few U3Si2 grains, some being even monocrystalline. The main secondary phase present in hyper-stoichiometric batches is an U20Si16C3-like phase. Other minor phases are also encountered, some of them containing metallic impurity elements. These features are attributed to the uranium raw material composition and to a slight contamination by carbon during the powder synthesis.The nature and morphology of secondary phases present in U3Si2 atomized particles appear thus to be linked not only to the silicon excess but also to the presence of impurities which probably strongly segregate during the very fast solidification of the alloy droplets. A slight superficial oxidation of particles also occurs and induces a local redistribution of silicon.

In-situ decarburization and deoxidation during laser powder bed fusion of water-atomized steel C35

Water atomization of low alloyed steels is a very cost-effective way to produce metal powders for laser powder bed fusion. In this study, water atomized C35 steel powder is used to 3D-print samples with different powder bed fusion machines. The porosity of the samples was analyzed. Chemical analysis of printed samples and the powder feedstock was carried out. The gas atmosphere during laser powder bed fusion process was measured to investigate changes in carbon and oxygen content of the samples. With optimal processing parameters, samples with a porosity of only 0.1% can be achieved. Gas atmosphere measurements have shown, that a reaction between carbon and oxygen in the melt pool occurs, leading to the formation of volatile carbon monoxide. By in-situ reduction of the oxygen and carbon level, negative effects caused by oxygen like balling of single melt tracks can be prevented to produce nearly dense parts. • Water-atomized C35 medium carbon steel powder was used for laser powder bed fusion • Samples with porosity of only 0.1% can be built using appropriate parameters • During LPBF, oxygen reacts with carbon inside of the melt pool • Volatile CO forms during LPBF to reduce carbon and oxygen content of samples • Excessive pore formation is prevented due to deoxidation during the process

Solidification behavior and porosity in electron-beam powder bed fusion of Co–Cr–Mo alloys: Effect of carbon concentrations

An increased carbon content strengthens Co–Cr–Mo alloys for use in a broad range of industrial applications. In this study, we investigated the influence of the carbon content (0.04–2.5 mass%) on the porosity and microstructure of Co–27Cr–6Mo (mass%) alloys during atomization and electron-beam powder bed fusion (EB-PBF). Quantitative X-ray computed tomography clarified that the volume fraction of pores in the raw powders monotonically increased with the carbon content, as a potential effect of the significant reduction in the liquidus temperature. In contrast, the porosity evolution in the investigated alloys during EB-PBF under identical building conditions suggested an influence of carbon concentration that was distinct from that in the powder. These alloys exhibited negligible porosity fraction for 0.04 and 0.22 mass% and a maximum volume fraction (∼0.3 vol.%) at 2.0 mass%, followed by a remarkable reduction caused by further carbon addition. The porosity of the as-built alloys could be correlated to the solidification behavior varying with carbon concentration. The smoother and more flat solidification front during the cellular (0.04 and 0.22 mass%) and eutectic (2.5 mass%) solidification could effectively eliminate the gas bubbles from the melt pool, whereas the complicated morphology at the solid–liquid interfaces during the dendritic growth (1.5 and 2.0 mass%) hindered the pore elimination in the melt pool. Adding carbon significantly increased the Rockwell hardness of the as-built specimens, reaching a significantly high value of HRC59 at 2.5 mass% of carbon, primarily due to the formation of hard carbide precipitates. The obtained findings could be beneficial to reduce entrapped gas pores thereby contributing to the development of highly durable metal components.

Production of gas-atomized powders of [(Fe0.6Co0.4)0.75B0.2Si0.05]96Nb4 glass-forming alloy and their consolidation by hot extrusion

The present work is focused on the production of gas-atomized powders of the [(Fe0.6Co0.4)0.75B0.2Si0.05]96Nb4 (at%) glass-forming alloy and their consolidation within the supercooled liquid interval by hot extrusion. The thermal history of the powders during gas atomization was modeled using momentum and energy conservation equations. While these calculations predicted that the atomized droplets were subjected to solidification rates over 103 K/s, some crystalline phases were still experimentally observed in the atomized powders. The crystalline structure of these phases was determined using synchrotron x-ray diffraction experiments. The atomized powders with diameters between 53 and 75 µm were encapsulated in copper cans and hot extruded at 565 °C using an extrusion ratio of 3:1. The extrusion produced deformed powders, suggesting that the process was successfully conducted between the glass transition and crystallization temperatures. Minimal crystallization occurred during consolidation, as quantified by optical microscopy and differential scanning calorimetry techniques. Nanocrystals of about 10 nm, dispersed in a glassy matrix, were observed in the extruded powders. Furthermore, a discontinuous layer of α-(Fe, Co) phase was present between the extruded particles. The presence of hard micro-size crystalline particles among the powders led to a highly heterogeneous flow during extrusion. Due to stress concentration at the interface between glassy and crystalline particles, cracks sometimes nucleated and grew along the boundaries between the extruded particles. The results shown in this work give an important contribution to the understanding of the effect of crystalline particles on the processing of metallic glass matrix composites within the supercooled liquid interval.

On the first hydrogenation kinetics and mechanisms of a TiFe0.85Cr0.15 alloy produced by gas atomization

This article reports the hydrogenation properties of a TiFe0.85Cr0.15 alloy prepared by gas atomization on one hand, and vacuum arc-remelting on the other hand for demonstration and reference, respectively. To evidence the excellent potential of ternary alloying combined with gas atomization process for improving the first hydrogen absorption kinetics, both the atomized powders and the reference crushed ingots were exposed to air from 1 h to as long as 10 days. In spite of the resulting surface oxide layer formation, all specimens still absorbed hydrogen partly thanks to the presence of the C14 Laves phase. As expected, the first hydrogenation kinetics decreased with increasing air-exposure time, but atomized powders not only outperformed the reference counterparts but also remained quite competitive despite surface oxidation. The remarkable kinetic enhancement observed was attributed to the formation of an additional Ti2Fe phase, to an increased amount of C14 Laves phase, as well as to a fine microstructure resulting from the rapid cooling rate involved in gas atomization. Even though different absorption behaviors were observed for all samples, the reaction mechanisms derived from solid-gas reaction models were ascribed to interface- and diffusion-controlled 3D processes in the early and subsequent stage of the first hydrogenation, respectively.

Laser powder bed fusion of an Al-Cr-Fe-Ni high-entropy alloy produced by blending of prealloyed and elemental powder: Process parameters, microstructures and mechanical properties

High-entropy alloys in the Al-(Co)-Cr-Fe-Ni system have been designed along several pathways to obtain tailored microstructures with remarkable mechanical properties, such as high strength and ductility. Additive manufacturing techniques, such as laser powder bed fusion, have been utilized and aim towards further optimization of their mechanical properties. However, processing challenges exist for these promising alloys, mainly due to their crack susceptibility as recently shown in the Co-free Al-Cr-Fe-Ni alloy. In this study, gas atomized prealloyed powder of a baseline Al-Cr-Fe-Ni high-entropy alloy was mixed with Fe and Ni elemental fine powder particles, to produce a powder blend with a modified composition. It was aimed to improve the alloy processability via designing the solidification path by reducing the Al content. The synthesized novel alloy composition was processed by laser powder bed fusion and crack-free material with a metastable, near single-phase face-centered cubic microstructure was obtained. Process parameters for minimum porosity were identified and net-shape tensile specimens were produced. Heat treatment led to a refined dual-phase microstructure consisting of face-centered cubic and body-centered cubic phases with promising mechanical properties, such as high tensile strength, reasonable elongation and notable strain hardening.

Fe-Based Amorphous Magnetic Powder Cores with Low Core Loss Fabricated by Novel Gas-Water Combined Atomization Powders.

FeSiBCCr amorphous powders were produced by a novel gas–water combined atomization process, and the corresponding MPCs (magnetic powder cores) were subsequently fabricated by phosphating treatment (0.4~1.6 wt.%), cold pressing (550~2350 MPa), and annealing (423~773 K), respectively. The results showed that the powders had high circularity, excellent thermal stability (ΔT = 59 K), and high saturation magnetization (0.83 T), which could provide raw powders for high-performance MPCs. With increasing phosphoric acid concentrations, despite the increase in DC-bias%, the uniformity of the insulation layers deteriorated, which led to a decrease in permeability and an increase in core loss. With increasing compaction pressures, the core loss increased continuously, and the permeability and DC-bias% first increased and then decreased. When annealing below the crystallization temperature, with increasing annealing temperatures, the permeability increased, and the core loss and DC-bias% decreased continuously. Under the optimized process of 0.4 wt.% phosphating concentration, 550 MPa pressure, and 773 K annealing temperature, the MPCs had a permeability of 21.54 ± 1.21, DC-bias% of 90.3 ± 0.2, and a core loss (Bm = 50 mT, f = 100 kHz) of 103.0 ± 26.3 mW cm−3. The MPCs had excellent high-frequency low-loss characteristics and showed great application potential under the development trends of high current, high power, and high frequency of electronic components.