• 제목/요약/키워드: Treatment Phase

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Strain Amplitude Dependence of Damping Capacity in Mg-AI-Si Alloy (Mg-Al-Si 합금에서 진동감쇠능의 변형진폭 의존성)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.24 no.3
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    • pp.144-148
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    • 2011
  • Change in damping capacity with strain amplitude was studied in Mg-Al-Si alloy in as-cast, solution-treated and aged states, respectively. The as-cast microstructure of the alloy is characterized by eutectic ${\beta}$($Mg_{17}Al_{12}$) phase and Chinese script type $Mg_2Si$ particles. The solution treatment dissolved the ${\beta}$ phase into the matrix, while the aging treatment resulted in the distribution of continuous and discontinuous type ${\beta}$ precipitates. The solution-treated microstructure showed better damping capacity than as-cast and aged microstructures both in strain-dependent and strain-independent damping regions. The decrease in second-phase particles which weakens the strong pinning points on dislocations and distribution of solute atoms in the matrix, would be responsible for the enhanced damping capacity after solution treatment.

PRECIPITAlON BEHAVIOR OF 8090 ALUMINIUM ALLOY BY HERMOMECANICAL AND DUPLEX AGING TREAMENT (가공열처리 및 2단시효처리에 의한 8090알루미늄 합금의 석출거동)

  • Lee, Hag-Yong;Kim, Sug-Woo;Woo, Kee-Do
    • Journal of the Korean Society for Heat Treatment
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    • v.7 no.4
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    • pp.270-276
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    • 1994
  • The effects of thermomechanical and duplex aging treatment on precipitation behavior were investigated for the 8090 aluminium alloy by tensile test, hardness test, plane-strain fracture toughness test and electron microscope. Both pre-aging stretch and duplex aging with pre-aging stretch were effective to homogenize the distribution of S' phase in this alloys. The latter makes more homogeneous distribution of S' phase than that of the former, but the sizes of S' phase in both specimens are almost same. The size and distribution of 0' phase were not changed by thermomechanical or duplex aging treatment. The strength was increased by thermomechanical treatment, but the elongation was decreased. Duplex aging treatment couldn't change the strength and elongation. Pre-aging stretch and duplex aging with pre-aging stretch have same effect on the strength and elongation. The increase of strength by thermomechanical treatment in 8090 alumunium alloy was caused by homogeneously precipitated S' phase.

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Microstructural Evolution in the Unidirectional Heat Treatment of Cu-35%Sn Alloys (Cu-35%Sn 합금의 일방향 열처리에서 출현하는 미세조직)

  • Choi, K.J.;Jee, T.G.;Park, J.S.
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.6
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    • pp.320-328
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    • 2003
  • A specimen of Cu-35%Sn alloy has been subjected to the unidirectional heat treatment in an attempt to examine the evolution of microstructures under varying thermal conditions. The specimen was cast in the form of a cylinder 10 mm in diameter and 200 mm in length, which was then installed in the temperature gradient field established inside a vertical tube furnace. The furnace temperature was adjusted to make the upper part at $750^{\circ}C$ and bottom end part at $300^{\circ}C$ of the specimen. The experiment was terminated by dropping it into water after the 30 minutes holding at given temperature. By the rapid cooling, the high temperature phases, ${\gamma}$ and ${\zeta}$, were retained at ambient temperature with some of ${\gamma}$ phase transformed to ${\varepsilon}$ phase, especially at the grain boundaries of ${\gamma}$ phase. The presence of ${\varepsilon}$ phase was found to determine the nature of phase transformations of the ${\zeta}$ phase undergoes upon cooling. In the close area of the ${\varepsilon}$ phase, ${\varepsilon}$ phase grew separately out of ${\zeta}$, and adds to the preexisting ${\varepsilon}$ whereas in areas away from ${\varepsilon}$, both ${\delta}$ and ${\varepsilon}$ grew simultaneously out of ${\zeta}$, and formed a lamella eutectoid structure. The transformation to ${\delta}$ was found to occur only in slow cooling. The hardness on each phase showed that the retained phases, ${\gamma}$ and ${\zeta}$, could be plastically deformed without brittle fracture while the phases, ${\varepsilon}$ and ${\delta}$, were too brittle to be deformed.

The Influence of Heat Treatment Temperature on Microstructure and Corrosion Behavior of SDSS Tube (SDSS (Super Duplex Stainless Steel) 강관의 미세조직 및 부식특성에 미치는 열처리 온도의 영향)

  • Lee, Insup;Cheon, Chang-seok;Yim, Tai-Hong;Han, Yoon-Ho;Lee, Myon-Hag
    • Journal of the Korean institute of surface engineering
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    • v.48 no.6
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    • pp.329-334
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    • 2015
  • The aim of this paper is to determine the proper heat treatment temperature for SDSS tube production without ${\sigma}$-phase precipitation. When Mother steel tube was heat treated at $800^{\circ}C$ temperature, relatively a large amount of ${\sigma}$-phase precipitated and grain refinement of ferrite phase occurred simultaneously. However, in Pilgered and Drawn steel tubes, grain refinement of the ferrite phase did not occur and a small amount of ${\sigma}$-phase precipitated. For all three types of steel tubes, the pitting potential was reduced to 2/5 or less compared with the untreated one and corrosion also occurred in the salt spray test due to the precipitation of ${\sigma}$-phase. When heat treatment temperature was $900^{\circ}C$, grain refinement of the ferrite phase occurred and very little ${\sigma}$-phase precipitated in Pilgered and Drawn steel tubes. But when heat treatment was done at $1,000^{\circ}C$ temperature, all three types of steel tubes had a similar corrosion properties of that of untreated one and also corrosion did not occur in the salt spray test, as ${\sigma}$-phase did not precipitate. Therefore, the optimum heat treatment temperature range is determined to be more than $1000^{\circ}C$ for the SDSS at which corrosion does not occur.

A Study on the Phase Formation Process in Bi-system Superconductor with Heat Treatment Conditions (열처리 조건에 따른 Bi계 초전도체에서 상 생성 과정에 대한 연구)

  • 정진인;이준웅;박용필
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.11a
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    • pp.221-223
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    • 1999
  • In this work, samples were manufactured variously by changing conventional calcining and sintering conditions and we tried the utilization by making the heat treatment time, which is demanded to high-Tc phase formation, much shorter. We found out optimal heat treatment conditions with the analysis on formation process at superconducting phase in term of the change of calcining and sintering time and then, examined X-ray diffraction(XRD) patterns, scanning electron microscope(SEM) measurement and energy dispersive X-ray spectrometer(EDX) of the samples manufactured under heat treatment conditions which we suggest here. As a result, 2223 high-$T_c$, phase of (Bi,Pb)SrCaCuO superconductor starting with ($Bi_l$ xPbx,)$_2$$Sr_2$$Ca_2$$Cu_3$$O_y$, composition was formed from 1 hr sintering sample at temperature nearby melting point and also the completed sample with calcining and sintering time of 9 hr was formed high-$T_c$.low-$T_c$ phase appearing in sight above the critical temperature of liquid $N_2$.

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Effect of the Heat treatment and Boron on the Hot Corrosion Resistance of the Al Diffusion Coating (Al 확산피복층의 고온 내식성에 미치는 후열처리와 B첨가의 영향)

  • 김태원;윤재홍;이재현;김현수;변응선
    • Journal of the Korean institute of surface engineering
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    • v.32 no.1
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    • pp.67-77
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    • 1999
  • The Ni base superalloy Mar-M247 substrate was aluminized or aluminized after boronizing by the pack cementation under Ar atmosphere. The hot corrosion resistance and after-heat-treatment effect of aluminized specimens were studied by the cyclic hot corrosion test in $Na_2SO_4$-NaCl molten salt. XRD analysis showed that the $Ni_2Al_3$ phase was formed between the coated layer and substrate below 1273K but the NiAl phase above 1273K. The peak of the NiAl phase was developed after heat treatment. Corrosion test showed that corrosion resistance of the specimen with the NiAl phase was better than that with the $Ni_2Al_3$ phase. Corrosion resistance could be improved by heat treatment to form ductile NiAl phase, where cracks were not formed by thermal shock on coating layer. Moreover, it appeared that heat treatment played a role to improve corrosion resistance of Al diffusion coating above 1273K. The existence of boron in the Al diffusion coating layer obstructed outwared diffusion of Cr from the substrate, and it influenced on corrosion resistance of the coating layer by weakening adherence of the oxide scale.

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Characteristic Change of PVDF-$SiO_2$ Composite Nanofibers with Different Thermal Treatment Temperature (열처리 온도에 따른 PVDF-$SiO_2$ 복합나노섬유의 특성 변화)

  • Kim, Young-Jin
    • Polymer(Korea)
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    • v.35 no.6
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    • pp.605-609
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    • 2011
  • Composite nanofibers were prepared by electrospinning and thermal treatment from poly (vinylidene fluoride) (PVDF)-$SiO_2$ blend solution. The nanofibers were stacked on layers to produce fully interconnected pores. TEM micrographs and EDX spectra confirmed the presence of $SiO_2$ in the composite nanofibers. The porosity of nanofibers was effectively enhanced by the introduction of electrospinning technique. ATR-FTIR and XRD results revealed that PVDF in the composite nanofibers exhibited the mixture crystal structure of ${\alpha}$-phase and ${\beta}$-phase. The crystal structure of ${\alpha}$-phase and crystallinity increased by the thermal treatment. In addition, the mechanical properties, thermal stability and hydrophobicity were markedly amplified by the thermal treatment.

Phase stability and Sintered Properties of 1.5mol% Yttria-stabilized Zirconia Ceramics Fabricated by Low Temperature Sintering (저온 열처리로 제작된 1.5 mol% 이트리아 안정화 지르코니아 세라믹스의 상 안정성 및 소결물성)

  • Kyung Tae Kim;Han Cheol Choe;Jeong Sik Park;Jong Kook Lee
    • Journal of the Korean Society for Heat Treatment
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    • v.37 no.1
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    • pp.1-8
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    • 2024
  • Phase stability of tetragonal crystals in yttria-stabilized zirconia ceramics is dependent on the content of yttria and the heat-treatment condition, related with mechanical properties. In this study, we fabricated the 1.5 mol% yttria-stabilized zirconia (1.5Y-YSZ) ceramics by cold isostatic pressing (CIP) and post-sintering at temperature range of 1200 to 1350℃ for 2 hours and investigated the sintered properties and microstructural evolution. Sintered and microstructural parameters, i.e, apparent density, grain size and phase composition of 1.5Y-YSZ ceramics were mainly dependent on the sintering temperature. Maximum sintered density of 99.4 % and average grain size of 200-300 nm could be obtained from the heat-treatment condition above sintering temperature at 1300℃ for 2 hours, possessing the superior mechanical hardness with 1200 Hv. However, phase stability of tetragonal grains in 1.5 YSZ ceramics is very low, inducing the phase transformation to monoclinic crystals on specimen surface during cooling after heat-treatment.

Effects of Low Temperature Plasma Nitriding Treatment on Mechanical Properties of Stainless Steel (스테인리스강의 기계적 성질에 미치는 저온 플라즈마 질화처리조건의 영향)

  • Bin, Jeonguk;Kim, Hangoon
    • Journal of the Korean Society for Heat Treatment
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    • v.23 no.5
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    • pp.269-276
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    • 2010
  • This study has been carried out to the low temperature plasma nitriding treatment on the mechanical properties of stainless steel at temperature range between $400^{\circ}C$ and $500^{\circ}C$. It was found that there was precipitated to free CrN matrix below $400^{\circ}C$ and there was precipitated S-phase of STS 316L, ${\varepsilon}$-phase of STS 409L and ${\alpha}N$-phase of STS 420J2. STS 316L has formed relatively abundant CrN phase and ${\gamma}^{\prime}-Fe_4N$ phase at $500^{\circ}C$, alternatively STS 409L and STS 420J2 were more deeply nitrided than STS 316L at $500^{\circ}C$.

Effect of Heat Treatment of powder on the Tribological Behavior of the Plasma Sprayed Zirconia Coating (분말 열처리가 지르코니아 용사코팅층의 마모특성에 미치는 영향)

  • 신종한;임대순;안효석
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2000.11a
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    • pp.298-303
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    • 2000
  • The 3 mol% yttria stabilized zirconia (3-Y PSZ) powder was heat treated at 50 0$^{\circ}C$ to evaporate the polymer binder and stabilize the tetragonal phase. The wear experiments were carried out on a ring-on-plate type reciprocating wear tester at selected temperatures with in the range room temperature to 600$^{\circ}C$ The results show that the heat treatment of powder decreases the wear rate due to the reduction of microcracks and pores in coatings and the stabilization of the tetragonal phase. Powder heat treatment enhanced the quality of the coating layer by removing remnant gases during coating process and the powder heat treatment at which tetragonal phase is stable diminished phase ratio of monoclinic. These two effects improved wear resistance characters.

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