• 열처리공학회지
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• 제28권3호
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• pp.126-133
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• 2015

The aim of this study is to investigate the effect of solution treatment on the corrosion behavior of Mg-8%Al-(0-1)%Zn casting alloys in 1M NaCl aqueous solution. After the solution treatment, all alloys showed single ${\alpha}$-(Mg) phase microstructure by dissolution of ${\beta}(Mg_{17}Al_{12})$ phase into the ${\alpha}$-(Mg) matrix. The $H_2$ evolution volume decreased with an increase in Zn content, which indicates that the addition of Zn plays a beneficial role in decreasing corrosion rate of the Mg-Al-Zn alloy in solution-treated state. The microstructural evaluations on the corrosion products and corroded surfaces after the immersion test in 1 M NaCl solution revealed that the incorporation of more $Al_2O_3$ and ZnO into the corrosion product, by which the penetration of $Cl^-$ ions is impeded, are thought to be responsible for the better corrosion resistance in relation with the Zn addition.

• 한국가구학회지
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• 제19권4호
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• pp.229-234
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• 2008

In a previous study, it was revealed that three major softwoods, Japanese pine, Korean pine and Japanese larch, heat-treated at $220^{\circ}C$, could produce high quality dark-colored boards. It is known that heat treatment decreases the hygroscopicity of wood. The hygroscopicity of major domestic softwoods and hardwoods heat-treated at $220^{\circ}C$ was investigated by a saturated salt solution method and compared with that of black and white charcoals. Equilibrium moisture contents of wood decreased with the increase of heat treatment time. Isotherm shapes of wood species were different from those of charcoals. Heat treatment decreases the equilibrium moisture contents of black locust more than those of Korean pine and Japanese larch. It was found that surface hardness of wood is improved by heat treatment to a certain extent, but a longer heat treatment causes thermal degradation, resulting in the decrease of the surface hardness.

• 열처리공학회지
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• 제26권4호
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• pp.185-190
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• 2013

Influence of solution treatment (T4) and peak-aging (T6) on damping capacity was investigated in permanent-mold cast Mg-3%Nd alloy. In as-cast state, the microstructure was characterized by eutectic $Mg_{12}Nd$ intermetallic phase network in the intergranular region. T4 treatment resulted in a dissolution of the eutectic particles, but small amount of the particles still remained in the microstructure. After T6 treatment, nano-sized ${\beta}^{\prime}(Mg_{12}Nd)$ particles were precipitated within the matrix. T4 microstructure showed higher damping capacity than as-cast and T6 ones. In view of the microstructural features, this may well be associated with the dissolution of second-phase particles which play a role in pinning the dislocations acting as a damping source.

• 한국표면공학회지
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• 제46권6호
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• pp.277-282
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• 2013

This study is an experimental attempt to confirm the binder effect of zeolite coating on glass plate by heat treatment. As a result, zeolite was successfully formed with low concentratios of pressure, whose concentration was effective in 10% or more for thin film zeolite coating. And as the content of the binder (TEOS) in mixed coating solution was higher, the zeolite was fastened better on the surface. Above 5% content of the binder in the coating solution, TEOS hindered zeolite synthesis of the precursor and brought to zeolite capacity decrease. Furthermore, when the concentration of the precursor, sedimentation rate of the precursor was higher and the coating efficiency is reduced thereby. Therefore, the most effective concentrations of the precursor and TEOS in the coating solution was 10% and 5%, respectively. It was concluded that zeolite coating is produced by heat treatment method after dipping without hydrothermal synthesis.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.407-414
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• 2014

Polyacrylonitrile (PAN) copolymers with different methyl acrylate (MA) contents were synthesized via solution polymerization and used as precursors for high-performance PAN ultrafine fibrids. The chemical structures of the copolymers were characterized using Fourier-transform infrared spectroscopy and $^{13}C$ nuclear magnetic resonance spectroscopy. Their particle sizes and aspect ratios increased with increasing viscosity, and the degree of crystallinity increased with decreasing concentration of copolymer solution. In contrast, their peak temperature and heat of exotherm increased with decreasing concentration of the copolymer solution. The aromatization indices (AIs) of the fibrids increased with increasing heat-treatment time; however, the AIs decreased when the heat-treatment temperature was higher than the onset temperature of the copolymers. On the other hand, the crystal sizes of the fibrids decreased with increasing concentration of the copolymer solution when the MA content was held constant.

• 열처리공학회지
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• 제7권4호
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• pp.253-261
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• 1994

Transformation behavior and superelastic behavior of Ti-Ni-Cu alloys with various Cu content has been investigated by means of electrical resistivity measurement, X-ray diffraction, tensile test and transmission electron microscopy. Two types of heat treatment are given to the specimens: i) Solutions treatment. ii) thermo-mechanical treatment. The transformation sequence in solution treated Ti-Ni-Cu Alloys substituted by Cu for Ni up to 5at.% occurs to $B2{\rightleftarrows}B19^{\prime}$ and it proceeds in two stages by addition of 10at.%Cu, i. e, $B2{\rightleftarrows}B19{\rightleftarrows}B19^{\prime}$. Also, it has been found that Ti-30Ni-20Cu alloy transformed in one stage : $B2{\rightleftarrows}B19$. The thermo-mechanically treated Ti-47Ni-3Cu alloy transformed in two stages: B2${\rightleftarrows}$rhomboheral phase${\rightleftarrows}B19^{\prime}$, while transformation sequence in Ti-45Ni-5Cu and Ti-40Ni-10Cu alloy transformed as same as solution treated specimens. The critical stress for inducing slip deformation in solution treated and thermo-mechanically treated Ti-40Ni-10Cu alloy is about 90MPa and 320Mpa respectively.

• 열처리공학회지
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• 제8권3호
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• pp.197-204
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• 1995

In recent work, we reported that a hot-rolled Fe-18wt%Mn alloy exhibited high damping capacity as well as excellent mechanical properties. It was also proposed that damping capacity of the alloy was proportional to the ${\gamma}/{\varepsilon}$ boundary area. In the present study, the effects of homogenization(12hrs at $1100^{\circ}C$) and solution treatment(1hr at $1050^{\circ}C$ before air cooling) on damping capacity and mechanical properties were investigated for as-cast and heat treated Fe-18wt%Mn alloy. The specimen subjected to both homogenization and solution treatment was found to show superior damping capacity and mechanical properties to the as-cast state due to removal of segregation and increase in ${\gamma}/{\varepsilon}$ boundary area.

• 열처리공학회지
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• 제19권1호
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• pp.3-9
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• 2006

The phase changes, nitride precipitation and hardness variations of 14%Cr-6.7Ni-0.65Mo-0.26Nb-0.05V-0.03C super martensitic stainless steel were investigated after nitrogen permeation heat treatment at a temperature range between $1050^{\circ}C$ and $1150^{\circ}C$. The nitrogen-permeated surface layer was transformed into austenite. The rectangular type NbN, NbCrN precipitates and fine round type precipitate were coexisted in the surface austenite layer, while the interior region that was free from nitrogen permeation kept the martensitic phase. The hardness of surface austenite showed 280 Hv, while the interior region of martensite phase represented 340 Hv. When tempering the nitrogen-permeated steel at $450^{\circ}C$, a maximum hardness of 433 Hv was appeared, probably this is attributed to the secondary hardening effect of the precipitates. The nitrogen concentration decreased gradually with increasing depth below the surface after showing a maximum of 0.3% at the outmost surface. The strong affinity between nitrogen and Cr enabled the substitutional element Cr to move from interiors to the surface when nitrogen diffuse form surface to the interior. Corrosion resistance of nitrogen permeated steel was superior to that of solution-anneaed steel in the solution of 1N $H_2SO_4$.

• 한국해양공학회지
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• 제22권4호
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• pp.46-50
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• 2008

Super duplex stainless steel has along life in severe environments because of its strength and corrosion resistance. If 0.2$\sim$0.3% Nitrogen in aninterstitial solid solution is added, the austenite structure is reinforced. This improves the solid solution hardening and the anticorrosionability. In this study, the mechanical properties and structures of the super duplex stainless steel with the 0.2% N additive were investigated to determine the effect of various volume fractions on the austenite phase. The various volume fractions and distributions of the austenite structure in the applied test specimens were obtained by changing the heat treatment temperature and cycle. The characteristics by amounts of the $\sigma$ phase obtained from the precipitation heat treatment were alsoinvestigated. From the results, when the austenite volume fraction increases, the tensile strength decreases and elongation increases. And the $\sigma$ phase was rapidly increased by increasing the heat treatment time. When the volume fraction of the $\sigma$ phase increased, tensile strength increased.

• 한국주조공학회지
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• 제36권6호
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• pp.195-201
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• 2016

The effects of Mg addition on heat treatment and mechanical properties of A356 alloy were investigated. With increased amounts of Mg addition to A356 alloy, the grain size decreased and eutectic Si was refined. And, this process can improve the mechanical properties. Solid solution heat treatment causes the spheroidizing of eutectic Si. In this study, although eutectic Si was refined with Mg addition, solid solution time increased from 2 hours to 6 hours with Mg addition, and aging time also increased, from 4 hours to 8 hours. After heat treatment, Mg2Si remained in a formation of Chinese script. And, Chinese script Mg2Si formed with Mg addition caused a reduction of the elongation of the alloys according to the stress concentration.