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1
Content available Effect of Electrode Induction Melting Gas Atomization Process on Fine Powder Yields: Continuous Metal Melt Flow
Wu Jialun, Xia Min, Wang Junfeng, Ge Changchun
Archives of Metallurgy and Materials
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2023
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Vol. 68, iss. 3
839--849
EN
Electrode induction melting gas atomization (EIGA) is a newly developed method for preparing ultra-clean metal powders, and is a completely crucible-free melting and atomization process. Based on conducted several atomization experiments, we found that the fine powder yields obtained during the EIGA process were greatly affected by the status of metal melt flow. While, continuous metal melt flow was beneficial for the yield of fine powders, it was in conflict with the principle described for the vacuum induction melting inert gas atomization (VIGA) process. To understand the critical role of continuous metal melt flow in the EIGA process, a computational fluid dynamics (CFD) approach was developed to simulate the gas atomization process. The D50 particle size of powder prepared by atomization under continuous liquid metal flow was about 70 μm, while that obtained by atomization under non-continuous liquid metal flow was about 100 μm. The diameter distribution results of numerical simulations agreed well with the experimental measurements, which demonstrated the accuracy of our simulation method. This study provides theoretical support for understanding the critical role of continuous metal melt flow and improving fine powder yields in the EIGA process.
2
Content available Effect of Deformation Temperature on the Magnetic Properties of PrFeB Alloy Fabricated by Gas Atomization
Cho Ju-Young, Song Myung-Suk, Choa Yong-Ho, Kim Taek-Soo
Archives of Metallurgy and Materials
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2021
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Vol. 66, iss. 4
955--958
EN
To form the fine micro-structures, the Pr17Fe78B5 magnet powders were produced in the optimized gas atomization conditions and it was investigated that the formation of the textures, microstructures, and the changes in the magnetic properties with increasing the deformation temperatures and rolling directions. Due to the rapid cooling system than the casting process, the homogenous microstructures were composed of the Pr-rich and Pr2Fe14B without any oxides and α-Fe and enables grain refinement. The pore ratios were 2.87, 1.42, and 0.22% at the deformation temperatures of 600, 700, 800°C, respectively in the rolled samples to align the c-axis which is the magnetic easy axis. Because Pr-rich phase cannot flow into the pore with a liquid state at low temperature, the improvement of pore densification was gradually observed with increasing deformation temperature. To confirm the magnetic decoupling effects of Pr2Fe14B phases by Pr-rich phases, the magnetic properties were investigated in rolled samples produced at the deformation temperature of 800°C. Although the remanent field is slightly decreased by 30%, the coercivity fields increased by about 2 times than that previous casted ingot. It is suggested that the gas atomization method can be suitable for fabricating grain refined and pure PrFeB magnets, and the plastic deformation conditions and rolling directions are a critical role to manipulate microstructure and magnetic properties.
3
Content available Influence of Spark Plasma Sintering Temperature on Microstructure and Tthermoelectric Properties of Cu-Doped Bi0.5Sb1.495Te3 Compound
Lee Chul-Hee, Dharmaiah Peyala, Song Jun-Woo, Jeong Kwang-Yong, Hong Soon-Jik
Archives of Metallurgy and Materials
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2020
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Vol. 65, iss. 3
1105--1110
EN
Due to air pollution, global warming and energy shortage demands new clean energy conversion technologies. The conversion of industrial waste heat into useful electricity using thermoelectric (TE) technology is a promising method in recent decades. Still, its applications are limited by the low efficiency of TE materials in the operating range between 400-600 K. In this work, we have fabricated Cu0.005 Bi0.5Sb1.495Te3 powder using a single step gas atomization process followed by spark plasma sintering at different temperatures (623, 673, 723, and 773 K), and their thermoelectric properties were investigated. The variation of sintering temperature showed a significant impact on the grain size. The Seebeck coefficient values at room temperature increased significantly from 127 μVK to 151 μV/K with increasing sintering temperature from 623 K to 723 K due to decreased carrier concentration. The maximum ZT values for the four samples were similar in the range between 1.15 to 1.18 at 450 K, which suggest these materials could be used for power generation in the mid-temperature range (400-600 K).
4
Content available Gas Atomization Parametric Study on the VIGA-CC Based Synthesis of Titanium Powder
Kim Dae-Kyeom, Kim Young-Il, Lee Hwaseon, Kim Young Do, Lee Dongju, Lee Bin, Kim Taek-Soo
Archives of Metallurgy and Materials
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2020
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Vol. 65, iss. 3
997--1000
EN
With the recent advancement in technology for titanium metal powder injection molding and additive manufacturing, high yield and good flowability powder production is needed. In this study, titanium powder was produced through vacuum induction melting gas atomization with a cold crucible, which can yield various alloy compositions without the need for material pretreatment. The gas behavior in the injection section was simulated according to the orifice protrusion length for effective powder production, and powder was prepared based on the simulation results. The gas distribution changes with the orifice protrusion length, which changes the location of the recirculation zone and production yield of the powder. The produced powders had a spherical morphology, and the content of impurities (N, O) changed with the injected-gas purity.
5
Content available Effects of Si Addition on Microstructure and Mechanical Properties of the Al Alloys with High Cr Content Prepared by Gas Atomization and SPS Processes
Kim Yong-Ho, Oh Ik-Hyun, Yoo Hyo-Sang, Park Hyun-Kuk, Lee Jung-Han, Son Hyeon-Taek
Archives of Metallurgy and Materials
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2020
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Vol. 65, iss. 3
1045--1049
EN
This research describes effects of Si addition on microstructure and mechanical properties of the Al-Cr based alloys prepared manufactured using gas atomization and SPS (Spark Plasma Sintering) processes. The Al-Cr-Si bulks with high Cr and Si content were produced successfully using SPS sintering process without crack and obtained fully dense specimens close to nearly 100% T. D. (Theoretical Density). Microstructure of the as-atomized Al-Cr-Si alloys with high contents of Cr and Si was composed multi-phases with hard and thermally stable such as Al13Cr4Si4, AlCrSi, Al8Cr5 and Cr3Si intermetallic compounds. The average hardness values were 703 Hv for S5, 698 Hv for S10 and 824 Hv for S20 alloy. Enhancement of hardness value was resulted from the formation of the multi-intermetallic compound with hard and thermally stable and fine microstructure by the addition of high Cr and Si using rapid solidification and SPS process.
6
Content available Effect of Temperature on the Plastic Deformability of Gas Atomized NdFeB Anisotropic Magnets
Cho Ju-Young, Choa Yong-Ho, Nam Sun-Woo, Rasheed Mohammad Zarar, Kim Taek-Soo
Archives of Metallurgy and Materials
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2020
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Vol. 65, iss. 4
1293--1296
EN
NdFeB anisotropic sintered permanent magnets are typically fabricated by strip casting or melt spinning. In this study, the plastic deformability of an NdFeB alloy was investigated to study the possibility of fabricating anisotropic sintered magnets using gas atomized powders. The results show that the stoichiometric composition Nd12Fe82B6 softens at high temperatures. The aspect ratio and orientation factor of Nd12Fe82B6 billets after plastic deformation were found to increase with increasing plastic deformation temperature, particularly above 800°C. This confirms that softening at high temperatures can lead to plastic deformation of Nd2Fe14B hard magnetic phases.
7
Content available Effect of Powder Size on the Microstructure and Magnetic Properties of Nd-Fe-B Magnet Alloy
Cho Ju-Young, Abbas Sardar Farhat, Choa Yong-Ho, Kim Taek-Soo
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 2
623--626
EN
Rare earth Nd-Fe-B, a widely used magnet composition, was synthesized in a shape of powders using gas atomization, a rapid solidification based process. The microstructure and properties were investigated in accordance with solidification rate and densification. Detailed microstructural characterization was performed by using scanning electron microscope (SEM) and the structural properties were measured by using X-ray diffraction. Iron in the form of α-Fe phase was observed in powder of about 30 μm. It was expected that fraction of Nd2 Fe14 B phase increased rapidly with decrease in powder size, on the other hand that of α-Fe phase was decreased. Nd-rich phase diffused from grain boundary to particle boundary after hot deformation due to capillary action. The coercivity of the alloy decreased with increase in powder size. After hot deformation, Nd2 Fe14 B phase tend to align to c-axis.
8
Content available The Effect of Gas Pressure on Powder Size and Morphology in The Production of AZ91 Powder by Gas Atomization Method
Akkaş M., Çetin T., Boz M.
Archives of Metallurgy and Materials
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2018
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Vol. 63, iss. 4
1587--1594
EN
In this study, the effect of gas pressure on the shape and size of the AZ91 alloy powder produced by using the gas atomization method was investigated experimentally. Experiments were carried out at 820°C constant temperature in 2-mm nozzle diameter and by applying 4 different gas pressures (0.5, 1.5, 2.5 and 3.5 MPa). Argon gas was used to atomize the melt. Scanning electron microscope (SEM) to determine the shape of produced AZ91 powders, XRD, XRF and SEM-EDX analysis to determine the phases forming in the internal structures of the produced powders and the percentages of these phases and a laser measuring device for powder size analysis were used. Hardness tests were carried out to determine the mechanical properties of the produced powders. The general appearances of AZ91 alloy powders produced had general appearances of ligament, acicular, droplet, flake and spherical shape, but depending on the increase in gas pressure, the shape of the powders is seen to change mostly towards flake and spherical. It is determined that the finest powder was obtained at 820°C with 2 mm nozzle diameter at 3.5 MPa gas pressure and the powders had complex shapes in general.
9
Content available Fabrication and Characterization of CoCrFeNiMn High Entropy Alloy Powder Processed by Gas Atomization
Park T. G., Lee S. H., Lee B., Cho H. M., Choi W. J., Kim B. S., Shin K. S., Kim T.-S.
Archives of Metallurgy and Materials
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2018
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Vol. 63, iss. 2
1055--1059
EN
In this study, precisely controlled large scale gas atomization process was applied to produce spherical and uniform shaped high entropy alloy powder. The gas atomization process was carried out to fabricate CoCrFeNiMn alloy, which was studied for high ductility and mechanical properties at low temperatures. It was confirmed that the mass scale, single phase, equiatomic, and high purity spherical high entropy alloy powder was produced by gas atomization process. The powder was sintered by spark plasma sintering process with various sintering conditions, and mechanical properties were characterized. Through this research, we have developed a mass production process of high quality and spherical high entropy alloy powder, and it is expected to expand applications of this high entropy alloy into fields such as powder injection molding and 3D printing for complex shaped components.
10
Content available Manufacturing of powders by the method of metal spraying from the liquid phase
Michalak M., Ambroziak A., Żegleń K.
Interdisciplinary Journal of Engineering Sciences
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2016
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Vol. 4, no. 1
38--41
EN
Object of interest in the article is the method of metal spraying from the liquid phase (gas atomization method). Process involves melting of metal alloy and its subsequent spraying with the stream of inert gas. The quality of obtained powders depends largely on the properly conducted spraying, which results in powders properties – such as volume distribution and size of particles. Therefore, gas atomization method and relevant powders properties are reviewed. Experimental part covered investigations of alloy of tin, antimony and copper from the point of view of their volume fractions and chemical composition. It was concluded that method of metal spraying from the liquid phase enables ease control of grains geometry and assure high quality of manufactured powders.
11
Content available Fabrication Of Zn4Sb3 Alloys By A Combination Of Gas-Atomization And Spark Plasma Sintering Processes
Dharmaiah P., Kim H.-S., Lee L. H., Hong S.-J.
Archives of Metallurgy and Materials
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2015
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Vol. 60, iss. 2B
1417--1421
EN
In this study, single phase polycrystalline Zn4Sb3 as well as 11 at.% Zn-rich Zn4Sb3 alloy having ε-Zn4Sb3 (majority phase) and Zn (minority phase) phases bulk samples produced by gas-atomization and subsequently consolidated by spark plasma sintering (SPS) process. The crystal structures were analyzed by X-ray diffraction (XRD) and cross-sectional microstructure were observed by the scanning electron microscopy (SEM). The internal grain microstructure of 11at.% Zn-rich Zn4Sb3 powders shows lamellar structure. Relative density, Vickers hardness and crack lengths were measured to investigate the effect of sintering temperature of Zn4Sb3 samples which are sintered at 653, 673 and 693 K. Relative density of the single phase bulk Zn4Sb3 sample reached to 99.2% of its theoretical density. The micro Vickers hardness of three different sintering temperatures were found around 2.17 – 2.236 GPa.
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