• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.866-872
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• 2009

The effects of magnetic powder thickness on electromagnetic wave absorption characteristics in Fe-6.5Si-0.9Cr (wt%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The atomized FeSiCr powders were milled by using attritor for 12, 24, and 36 h, powder thickness changed from $40{\mu}m$ to $3{\mu}m$ upon 36 h milling. The composite sheet, including thinned magnetic flakes, exhibited higher power loss in the GHz frequency range as compared with the sheets having thick flakes. Moreover, both the complex permeability and the loss factor increased with the decrease in thickness of the alloy flakes. Therefore, the enhanced power loss property of the sheets containing thin alloy flakes was attributed to the flakes of high complex permeability, especially their imaginary part. Additionally, the complex permittivity was also increased with the reduction of flake thickness, and this behavior was considered to be helpful for improvement of the electromagnetic wave absorption characteristics in the composite sheets, including thin alloy flakes.

• Archives of Metallurgy and Materials
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• v.66 no.3
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• pp.759-763
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• 2021

The effects of the sintering holding time and cooling rate on the microstructure and mechanical properties of nanocrystalline Fe-Cr-C alloy were investigated. Nanocrystalline Fe-1.5Cr-1C (wt.%) alloy was fabricated by mechanical alloying and spark plasma sintering. Different process conditions were applied to fabricate the sintered samples. The phase fraction and grain size were measured using X-ray powder diffraction and confirmed by electron backscatter diffraction. The stability and volume fraction of the austenite phase, which could affect the mechanical properties of the Fe-based alloy, were calculated using an empirical equation. The sample names consist of a number and a letter, which correspond to the holding time and cooling method, respectively. For the 0A, 0W, 10A, and 10W samples, the volume fraction was measured at 5.56, 44.95, 6.15, and 61.44 vol.%. To evaluate the mechanical properties, the hardness of 0A, 0W, 10A, and 10W samples were measured as 44.6, 63.1, 42.5, and 53.8 HRC. These results show that there is a difference in carbon diffusion and solubility depending on the sintering holding time and cooling rate.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.106-111
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• 2008

In this paper, study about property evaluation for the metal matrix composites fabricated by low pressure infiltration process. Aluminum alloy composite which is reinforced by Metal fiber preform was fabricated by low pressure casting process. Infiltration condition was changed the pressure infiltration time of 1 sec, 2 sec and 5 sec under a constant pressure of 0.4 MPa. The molten alloy completely infiltrated the FeCrSi metal perform regardless of the increase in the pressure acceleration time. The the porosity in the FeCrSi/AC8A composite was investigated. The porosity was reduced as the pressure acceleration time as shorter. The FeCrSi/AC8A composite was investigated the wear test for to know the relationship between Porosity and wear resistance. FeCrSi/AC8A composite at pressure acceleration time of 1sec is shown excellent wear resistance.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.595-600
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• 2018

This study investigates the microstructural properties of CoCrFeMnNi high entropy alloy (HEA) oxynitride thin film. The HEA oxynitride thin film is grown by the magnetron sputtering method using nitrogen and oxygen gases. The grown CoCrFeMnNi HEA film shows a microstructure with nanocrystalline regions of 5~20 nm in the amorphous region, which is confirmed by high-resolution transmission electron microscopy (HR-TEM). From the TEM electron diffraction pattern analysis crystal structure is determined to be a face centered cubic (FCC) structure with a lattice constant of 0.491 nm, which is larger than that of CoCrFeMnNi HEA. The HEA oxynitride film shows a single phase in which constituting elements are distributed homogeneously as confirmed by element mapping using a Cs-corrected scanning TEM (STEM). Mechanical properties of the CoCrFeMnNi HEA oxynitride thin film are addressed by a nano indentation method, and a hardness of 8.13 GPa and a Young's modulus of 157.3 GPa are obtained. The observed high hardness value is thought to be the result of hardening due to the nanocrystalline microstructure.

• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.125-130
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• 1998

13Cr-1.5Nb-Fe alloy powder was fabricated by water atomization method, and ring-shape specimen of this composition was fabricated by oil press, and then sintered in the vacuum furnace. Powder shape, size distribution, composition (C, N, O, S) analysis and saturation magnetization of as-prepared 13Cr-1.5Nb-Fe alloy powder were investigated. Ac permeability and power loss was measured after forming and sintering process. Saturation magnetization and contents of oxygen of the alloy powder is160 emu/g and about 6000 ppm, respectively. 50 % volume fraction indicate particle size of 70$\mu$m. The ac permeability of sintered specimen increases with increasing sintering temperature and forming pressure. The power loss is 107 W/cc at sintering temperature of 1200 $^{\circ}C$, 12 ton/$\textrm{cm}^2$ forming pressure, and 20 KHz. It is the lowest among the prepared specimen.

• Journal of Powder Materials
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• v.12 no.1
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• pp.43-50
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• 2005

Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to Al-Fe-Cr and Al-Fe-Mo powder mixture to investigate effects of Cr and Mo addition on thermal stability of Al-Fe, and thereby to enhance its thermal stability up to $500^{\circC}$. Various analytical techniques including micro-Vickers hardness test, SEM, TEM, X-ray diffractometry and corrosion test were carried out. It was found that addition of Cr and Mo to Al-Fe system played a role of grain growth inhibitor of matrix Al and some precipitates such as $Al_3Fe$ during SPS and subsequent heat treatment. The inhibition of grain growth resulted in increased Vickers hardness and thermal stability up to $500^{\circC}$ comparing to those of Al-Fe alloy system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.385-388
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• 2009

Dry-sliding-wear behavior of Fe-18Cr-l0Mn steel with various carbon and nitrogen contents was characterized, and the effect of carbon and nitrogen contents on the wear was investigated. Dry sliding wear tests of the steel were carried out at room temperature against an AISI 52100 bearing steel ball using a pin-on-disk wear tester. Applied wear loads were varied from 10 N to 100 N, and the sliding distance was fixed as 720 m. Worn surfaces and the wear debris of the steel were examined using an SEM to find out the wear mechanism. It was found that the Fe-18Cr-10Mn with both carbon and nitrogen exhibited superior wear resistance to the steel with only nitrogen. The wear resistance of the Fe-18Cr-10Mn-xC-yN alloy increased with the increase of the carbon content. The excellent wear resistance of the Fe-18Cr-10Mn-xC-yN alloy was explained by the increased strain-hardening capability with the interstitial atoms.

• Advances in materials Research
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• v.6 no.4
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• pp.343-348
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• 2017

High-pressure gas atomization was employed to prepare the Fe-based $Fe_{50}Cr_{24}Mo_{21}Si_2B_3$ alloy powder. The effect of flow rate of atomizing gas on the median powder diameter was studied. The results show that the powder size decreased with increasing the flow rate of atomizing gas. Fe-based alloy coatings with amorphous phase fraction was then prepared by high velocity oxygen fuel spraying (HVOF) of gas atomized $Fe_{50}Cr_{24}Mo_{21}Si_2B_3$ powder. Microstructural studies show that the coatings present dense layered structure and low porosity of 0.17% in about $200{\mu}m$ thickness. The Fe-based alloy coating exhibits an average hardness of about 1230 HV. Our results show that the HVOF process results in dense and well-bonded coatings, making it attractive for protective coatings applications.

• Journal of Surface Science and Engineering
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• v.35 no.1
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• pp.5-10
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• 2002

This study was performed to investigate the influence of spraying condition to the coating layer properties of Fe-Cr-Ni-Mo-Si-B alloy using the HVOF. The investigations, such as thickness measurement, surface roughness, hardness, friction coefficient, resistance of corrosion were carried out. Matrix is prepared by gritting and coating layer is made of Fe-Cr-Ni-Mo-Si-B alloy powder using HVOF. Alumina gritting layers are superior to steel gritting layers. The less spaying distance, the more coating layer properties confirmed. The optimum spraying condition, in this study, was proved as 13inch spraying distance with feed rate 350rpm (78g/min).

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.1
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• pp.49-54
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• 1989

The purpose of this study was to investigate the interfacial elemental change when solding the Ni-Co-Cr dental removable partial denture alloy and Fe-Cr-Ni wrought wire alloy with Ag-Cu-Zu Silver solder, by EDXA, EPMA, to investigate the appropriateness of clinical usefullness for repair the fractured clasps of removable partial dentive. The result of this study was as follows: 1. The Ni element of major component of Ticonium penetrate into the silver solder 2. The movement Age element of silver solder into Fe-Cr-Ni wire was not significant, by EDXA and EPMA.