Journal of Powder Materials

[Korean]
Sintering Behavior and Microstructures of Tantalum and Tantalum-Tungsten Alloys Powders: Youngmoo Kim, Sung Ho Yang, Seong Lee, Sung Ho Lee, Joon-Woong Noh; J Korean Powder Metall Inst. 2020;27(5):373-380. Published online October 1, 2020; DOI: https://doi.org/10.4150/KPMI.2020.27.5.373

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The purpose of this study is to investigate the densification behavior and the corresponding microstructural evolution of tantalum and tantalum-tungsten alloy powders for explosively formed liners. The inherent inhomogeneous microstructures of tantalum manufactured by an ingot metallurgy might degrade the capability of the warhead. Therefore, to overcome such drawbacks, powder metallurgy was incorporated into the near-net shape process in this study. Spark plasma-sintered tantalum and its alloys with finer particle sizes exhibited higher densities and lower grain sizes. However, they were contaminated from the graphite mold during sintering. Higher compaction pressures in die and isostatic compaction techniques also enhanced the sinterability of the tantalum powders; however, a full densification could not be achieved. On the other hand, the powders exhibited full densification after being subjected to hot isostatic pressing over two times. Consequently, it was found that the hot isostatic-pressed tantalum might exhibit a lower grain size and a higher density as compared to those obtained in previous studies.

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Understanding the phase evolution and elemental distribution in MoWTaNbVTix manufactured via powder metallurgical approach
Surya T. Bijjala, Ryan Wilkerson, Chad Beamer, Pankaj Kumar
The International Journal of Advanced Manufacturing Technology.2024; 135(11-12): 5925. CrossRef
Thermal Stability and Weight Reduction of Al0.75V2.82CrZr Refractory High Entropy Alloy Prepared Via Mechanical Alloying
Minsu Kim, Hansung Lee, Byungmin Ahn
journal of Korean Powder Metallurgy Institute.2023; 30(6): 478. CrossRef

[Korean]
Characterization of Hot Isostatically Pressed Ni-Based Superalloy IN 713C: Youngmoo Kim, Eun-Pyo Kim, Seong-Taek Chunga, Seong Lee, Joon-Woong Noh, Sung Ho Lee, Young-Sam Kwon; J Korean Powder Metall Inst. 2013;20(4):264-268.; DOI: https://doi.org/10.4150/KPMI.2013.20.4.264

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Abstract PDF

Nickel-based superalloy IN 713C powders have been consolidated by hot isostatic pressing (HIPing). The microstructure and mechanical properties of the superalloys were investigated at the HIPing temperature ranging from 1030°C to 1230°C. When the IN 713C powder was heated above gammaprime solvus temperature (about 1180°C), the microstructure was composed of the austenitic FCC matrix phase gamma plus a variety of secondary phases, such as gammaprime precipitates in gamma matrix and MC carbides at grain boundaries. The yield and tensile strengths of HIPed specimens at room temperature were decreased while the elongation and reduction of area were increased as the processing temperature increased. At 700°C, the strength was similar regardless of HIPing temperature; however, the ductility was drastically increased with increasing the temperature. It is considered that these properties compared to those of cast products are originated from the homogeneity of microstructure obtained from a PM process.

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Sintering and Microstructures of SUS 316L Powder Produced by 3D Printing Process
W.J. Kim, H.-H. Nguyen, H.Y. Kim, M.-T. Nguyen, H.S. Park, J.-C. Kim
Archives of Metallurgy and Materials.2017; 62(2): 1215. CrossRef

[Korean]
Microstructural Evolution during Hot Deformation of Molybdenum using Processing Map Approach: Young-Moo Kim, Sung-Ho Lee, Seong Lee, Joon-Woong Noh; J Korean Powder Metall Inst. 2008;15(6):458-465.; DOI: https://doi.org/10.4150/KPMI.2008.15.6.458

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The hot deformation characteristics of pure molybdenum was investigated in the temperature range of 600sim1200°C and strain rate range of 0.01sim10.0/s using a Gleeble test machine. The power dissipation map for hot working was developed on the basis of the Dynamic Materials Model. According to the map, dynamic recrystallization (DRX) occurs in the temperature range of 1000sim1100°C and the strain rate range of 0.01sim10.0/s, which are the optimum conditions for hot working of this material. The average grain size after DRX is 5µm. The material undergoes flow instabilities at temperatures of 900sim1200°C and the strain rates of 0.01sim10.0/s, as calculated by the continuum instability criterion.

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Hot Deformation Constitutive Analysis and Processing Maps of Ultrasonic Melt Treated A5052 Alloy
Sun-Ki Kim, Seung-Hyun Koo, Hoon Cho, Seong-Ho Ha
Materials.2024; 17(13): 3182. CrossRef
Microstructural Evolution during Hot Deformation of P/M Copper using Processing Map
Soo-Ho Chang, Young-Moo Kim, Kyung-Chae Park
Journal of Korean Powder Metallurgy Institute.2012; 19(2): 134. CrossRef

[Korean]
Application of Refractory Metal Powders to Military Material Fields: Young-Moo Kim, Eun-Pyo Kim, Seong Lee, Joon-Woong Noh; J Korean Powder Metall Inst. 2007;14(4):221-229.; DOI: https://doi.org/10.4150/KPMI.2007.14.4.221

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Synthesis and Nucleation Behavior of MoO₃ Nano Particles with Concentration of Precursors
Seyoung Lee, Namhun Kwon, Jaeseok Roh, Kun-Jae Lee
Journal of Korean Powder Metallurgy Institute.2020; 27(5): 394. CrossRef
Fabrication of Ultra Fine Grained Molybdenum and Mechanical Properties
Se-Hoon Kim, Young-Ik Seo, Dae-Gun Kim, Myung-Jin Suk, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2010; 17(3): 235. CrossRef

[Korean]
A Study on the Reduction Mechanism of Tungsten and Copper Oxide Composite Powders: Seong Lee, Moon-Hee Hong, Eun-Pyo Kim, Sung-Ho Lee, Joon-Woong Noh; J Korean Powder Metall Inst. 2003;10(6):422-429.; DOI: https://doi.org/10.4150/KPMI.2003.10.6.422

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Abstract PDF: The reduction mechanism of the composite powders mixed with WO_3 and CuO has been studied by using thermogravimetry (TG), X-ray diffraction, and microstructure analyses. The composite powders were made by simple Turbula mixing, spray drying, and ball-milling in a stainless steel jar with the ball to powder ratio of 32 to 1 at 80 rpm for 1 h without process controlling agents. It is observed that all the oxide composite powders are converted to W-coated Cu composite powder after reducing treatment under hydrogen atmosphere. For the formation mechanism of W-coated Cu composite powder, the sequential reduction steps are proposed as follows: CuO contained in the ball-milled composite powder is initially reduced to Cu at the temperature range from 200°C to 300°C. Then, WO_3 powder is reduced to W O_2 via W O_2.9 and W O_2.72 at higher temperature region. Finally, the gaseous phase of WO_3(OH)_2 formed by reaction of WO_2 with water vapour migrates to previously reduced Cu and deposits on it as W reduced by hydrogen. The proposed mechanism has been proved through the model experiment which was performed by using Cu plate and WO_3 powder.

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