• The korean journal of orthodontics
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• v.22 no.3 s.38
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• pp.557-578
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• 1992

Heat treatment which removes internal stress enhances the mechanical properties of the orthodontic arch wire. The main purpose of this experiment was to investigate the effects of the heat treatment on the mechanical properties of the Elgiloy wire. The Elfiloy wire, 0.016' X 0.022' and 0.018' X 0.025', were heat treated in an electric oven for 5, 10 and 15 minutes at selected temperatures between 300 and $900^{\circ}C$. Tensile strength and load deflection rate were measured to reveal the changes of mechanical property at various conditions, and each specimen was observed under metallurgic microscope. Also to trace the precipitation material due to overheat treatment, a qualitative analysis was carried out with EDS system. It was found that heat treatment at a low temperature caused an increase in the tensile strength and bending resistance, and a maintenance in the fibrous in the tensile strength and bending resistance, and a maintenance in the fibrous structure of both sizes of wire. The changes observed in properties and appearance were probably due to the relief of internal stresses incurred in the metal during cold working. In both sizes of wire the tensile strength and the bending resistance continued to decrease at high temperature, and the fibrous structure continued to disappear then was not observed at $900^{\circ}C$. The carbide precipitation founded in grain boundary at $750^{\circ}C$ probably was other elements carbide (Ni, Co) except Cr. The grain growth was observed at $1100^{\circ}C$. Optimum heat treatment for the 0.016' X 0.022' Elgiloy wire was 10 minutes at $500^{\circ}C$, and for the 0.018' X 0.025' Elgiloy wire it was 5 to 15 minutes at $500^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.6
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• pp.412-419
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• 2000

There has been a considerable attention on Invar alloys due to its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than $10^{-6}$ near the room temperature, is attractive for electric transmission lines and precision machine tools. However, the expansion property of Invar alloys is limited below about 520K, and mechanical properties are relatively low to apply to electric transmission line. In order to improve mechanical properties in this alloy, Ti alloying element was added to the $Ni_{38}-Mo_2-Cr_1-Fe$ invar alloy. The microstructure Ti added alloy showed finer than that of the unalloyed one. It was found that the (Mo, Ti), Mo carbide formed by Ti addition obstacled grain growth by pinning effect and supplyed recrystallization sites during heat-treatment. Optimum heat-treatment conditions with Ti addition were also discussed in the modified Invar alloy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.73-76
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• 2003

Phase transformation of Bi-2223 tape during the final heat treatment has been investigated through the various duration time of heat treatment in a specially designed 3-step heat treatment. It was found that the phase assemblage in the sintering was determined by the sintering time and temperature. In this study, sintering time was changed to optimize the Bi-2223 phase assemblage, and acquire high critical current density. High critical current samples with Ic = 85 A and Je = 8.9 kA/$cm^2$ have been measured at 77K and self-field for 55-filament tapes sintered by optimum condition.

• Journal of Korea Foundry Society
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• v.41 no.4
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• pp.331-341
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• 2021

The effects of austempering temperature, austenitizing temperature and time, added copper content and prior heat-treatment on the processing window of 3.6wt%C-2.5wt%Si ductile cast iron during austempering. The maximum processing window was obtained at 350℃ of austempering temperature. The processing window was increased with increased austenitizing temperature from 850 to 900℃; however, it decreased at 950℃. The processing window was increased with increased austenitizing time from 0.5 to 2 hours and rather decreased for 4 hours. The optimum condition of austenitizing was obained at 900℃ for 2 hours. The processing window was increased with copper content added in the range of 0.0~0.8wt%. The processing window was increased by prior normalizing heat-treatment and decreased by prior annealing in comparison with that for the as-cast state,

• Journal of the Korean Ceramic Society
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• v.12 no.2
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• pp.26-30
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• 1975

The experiment has been carried out to clarify the condition of acid treatment for preventing the crack formation caused by swelling and shrinking during acid leaching process. The borosilicate glass contained phosphorous pentoxide was chosen as the sample, which is recognized to be more homogeneous in phase separation. The various effects, such as kind, cocentration and acid temperature, were investigated. The experimental results are summerized as follows. (1) Sulfuric acid is more stable than hydrochrolic acid for preventing the crack. (2) The optimum concentration of acid lies in the range of 0.1~0.3N. (3) Higher temperature of the acid to treat the separated glass was more stable than lower temperature. (4) The rate of crack decreased with the longer period and the higher temperature of the heat treatment.

• Carbon letters
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• v.2 no.3_4
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• pp.182-191
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• 2001

Quinoline insoluble formed by the heat treatment was hot-pressed near its softening point. The green body was stabilized in the temperature range of $300{\sim}400^{\circ}C$ and subsequently carbonized below $1300^{\circ}C$ in an argon atmosphere. The behaviors of QI formation was examined with varying the heat treatment temperature and the lapse of time of the sample carbonized at various temperatures. And the mechanical property, corrosion resistance, and friction behavior were also measured optimum content of mesophase pitch ensured a dense structure and high $LC_{(002)}$ value, which resulted in high mechanical properties, good corrosion resistance, and low-stable friction behavior.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.84-89
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• 1992

The polycrystalline $CuInS_2$ thin films are prepared by vacuum heat treatment of layer, which is deposited by vaccum evaporation in order. The electrical and optical properties of the films are investigated at various sulfur deposition mole rate, substrate temperature, heat treatment temperature and time. From data, n type-$CuInS_2$ exhibits resistivity, transmittance and energy band gap with 142[${\Omega}{\cdot}cm$], 73[%], and 1.5[eV] respectively at optimum fabrication condition. Finally, the films are fabricated with chalcoprite structure.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.3
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• pp.57-62
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• 2014

In this work, molybdenum oxide films were fabricated by heat-treatment method. Fundamental surface characteristics of molybdenum oxide films were investigated using XRD and Raman spectroscopy. From the results, the optimum MoOx films could be obtained under the conditions of thermal treatment temperature of $550^{\circ}C$, oxidation time of 30 minutes and oxygen flow rate of 250sccm. The thermal treatment method offers a simple and effective route for the synthesis of uniform $MoO_3$ films.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.263-270
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• 2012

This study investigates the effect of heat treatment on the mechanical properties of a forged Ni-based superalloy called Nimonic 80A. Nimonic 80A ingot samples were fabricated by vacuum spray casting to achieve a fine and homogenized microstructure. The ingot samples were subsequently hot-forged with the diameter of 220 mm at 1373 K. From the center to the surface of the forged Nimonic 80A, its average grain size decreased and its micro-Vickers hardness increased slightly. Solution treatment was carried out at 1353 K with 8 hours of air cooling followed by aging treatment, which was carried out in the range of 873-1073 K with various times from 0.5 to 256 hours. To set the optimum aging conditions, micro-Vickers hardness tests were performed. The maximum hardness value of 388.0 Hv was obtained by aging at 973 K for 32 hours. Also, tensile tests were performed for optimum aging conditions at room temperature and 873 K. The results can be used effectively to perform reasonable heat treatment of Nimonic 80A superalloy.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.233-238
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• 2021

The mechanical, anti-tarnishing, and corrosion characteristics of Yuggi (Cu-22wt%Sn) alloy are greatly affected by fraction of constituent phases according to heat treatment method. The Yuggi heat-treated at 750℃ has a β1' phase of 98% or more, which is a high-temperature disordered beta phase, on the other hand, cast Yuggi that Sn is solid-solutioned into Cu consists with α-phase over 60v/o. This difference of constituent phases of Yuggi may cause a difference in dissolution of Cu under antimicrobial test condition. Nonetheless, few studies have been conducted on the effect of fraction of constituent phases and constituent phases in antimicrobial activity. In addition, few studies have also been conducted on the suitable method measuring the antimicrobial activity of Yuggi. Hence, the purpose of this study is to provide an optimum measurement method of antimicrobial activity, and to evaluate quantitatively the effect of constituent phases on antimicrobial activity.