• Title/Summary/Keyword: Aging Heat-Treatment

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Effect of σ-phase on Intergranular Corrosion of Super Duplex Stainless Steel Weld Metal (슈퍼듀플렉스강 용접금속의 입계부식에 미치는 σ 상의 영향)

  • Lee, Jae-Hyoung;Jung, Byong-Ho;Seo, Gi-Jeong;Kang, Chang-Yong
    • Journal of the Korean Society for Heat Treatment
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    • v.26 no.6
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    • pp.293-299
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    • 2013
  • A specimen of weld metal was prepared by GTA welding with weld wire of super duplex stainless steel. Aging treatment was conducted for the sample at the temperature range of 700 to $900^{\circ}C$ for 5 to 300 minutes. The effect of volume fraction of ${\sigma}$-phase to intergranular corrosion of weld metal has been investigated and the results were derived as follows. The volume fraction of ${\sigma}$ phase tends to increase with an increase of aging temperature and time and intergranular corrosion of weld metal was increased by an increase of ${\sigma}$ phase. Degree of sensitization representing intergranular corrosion was found to tend to increase with an increase of aging time at 700 to $800^{\circ}C$, while it decreased by an increase of aging time at $900^{\circ}C$.

Effect of Tungsten-Substitution on the Corrosion Resistance of 2205 Duplex Stainless Steel (2205 2상 스테인리스강의 내식성에 미치는 텅스텐 치환의 영향)

  • 김기엽;안용식;정병호
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.6
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    • pp.704-713
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    • 2003
  • The effect of partial substitution of tungsten for molybdenum on the microstructure and corrosion resistance in 22Cr-5Ni-3Mo duplex stainless steel(DSS) aging heat treated in a temperature range of 600~$1000^{\circ}C$ has been investigated. Electrochemical tests were carried out for the evaluation of corrosion resistance. Aging treatment had hardly influenced the general corrosion resistance. With the increase of aging time, the pitting corrosion resistance of the DSS had decreased, After aging for 2min at 700~$900^{\circ}C$, the pitting potential of the 3Mo steel decreased remarkably, while that of the W-substituted steel hardly changed. During aging. the intermetallic $\sigma$ and secondary austenite ($\gamma_2$) phases were precipitated. and the pitting corrosion and intergranular corrosion resistance were significantly decreased after aging at 700~$750^{\circ}C$ for 10 h, which could be caused by the $\gamma_2$ formation. The ${\gamma}$$_2$ phase could affect the depletion of molybdenum and chromium in the $\gamma_2/\alpha and \gamma_2/\sigma$ boundaries.

Effect of Heat Treatment on the Mechanical Properties of Investment Casting Turbo Charger Wheel using A356 Alloy (A356합금을 이용한 정밀주조 Turbo Charger Wheel의 기계적 특성에 미치는 열처리의 영향)

  • Kim, Sang-Mi;Woo, Kee-Do;Kim, Ji-Young;Kim, Sang-Hyuk;Park, Sang-Hoon;Kang, Hwang-Jin;Park, Chan-Sung
    • Journal of Korea Foundry Society
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    • v.31 no.5
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    • pp.262-266
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    • 2011
  • The aim of this study is to investigate aging behavior of A356 alloy for turbo charger part. The specimen was fabricated by investment casting. Solution heat treatment was performed at $525^{\circ}C$ for 8h and followed by aging treated at $160^{\circ}C$, $170^{\circ}C$ for 0.5~20h. And their microstructures and mechanical properties of the aged specimens were analyzed by scanning electron microscope and hardness tester, respectively. All the cast A356 alloy included eutectic Si particles. In the cast A356 alloy, eutectic Si phase mainly was formed along Chinese script phase. Vickers hardness of the cast was improved by aging treatment due to formation of ${\beta}$" phase and ${\beta}$' phase.

Aging Behaviors of a Rapidly Solidified AI-Li-Cu Alloy (급냉응고된 Al-Li-Cu 합금의 시효거동)

  • Hong, Y.J.;Kim, S.H.;Kang, M.C.;Kim, I.B.
    • Journal of the Korean Society for Heat Treatment
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    • v.6 no.3
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    • pp.138-143
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    • 1993
  • Effects of aging treatment on the microstructural evolution of a rapidly solidified Al-Li-Cu alloy were investigated by differential scanning calorimetry (DSC) and transmission electron microscopy(TEM). It was found that the precipitation sequence was: supersaturated solid solution ${\alpha}^{\prime}$ ${\rightarrow}$ metastable ${\delta}^{\prime}$ + stable precipitate $T_1$ ${\rightarrow}$ stable precipitates ${\delta}+T_1$. Two exothermic and two endothermic peaks are detected by DSC analysis. The two exothermic and endothermic peaks corresponded to ${\delta}^{\prime}$ and ${\delta}+T_1$ precipitation and dissolution reactions respectively. The enthalpy of ${\delta}^{\prime}$ precipitation decreased with increasing of aging temperature and time until the finishing point of precipitation. The activation energy for precipitation of ${\delta}^{\prime}$ was measured as 80KJ/mol and the energy for dissolution was 93KJ/mol. These values arc higher than those of AI-Li binary alloy. Peak hardness value (Hv 170) was obtamed at $210^{\circ}C$ for 1hr aging treatment which coincided with finishing point of ${\delta}^{\prime}$ precipitation.

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Defensive Behavior against Noxious Heat Stimuli Is Declined with Aging Due to Decreased Pain-Associated Gene Expression in Drosophila

  • Ghimire, Saurav;Kim, Man Su
    • Biomolecules & Therapeutics
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    • v.23 no.3
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    • pp.290-295
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    • 2015
  • Aging is defined as a collective process that alters organism's functional capacity and appearance over the course of life. Apart from an increase in susceptibility to many diseases, aging affects the cellular system that is responsible for decoding painful stimuli. Yet, aging-associated molecular mechanisms of pain perception remains elusive. Using Drosophila, we showed a decrease in temperature tolerance and a reduction in high temperature thermal avoidance with aging. Locomotor activity assay demonstrated that the age-dependent changes in heat nociception did not stem from the general decline in muscular activity. However, we identified pain-related gene expression alteration with aging. We anticipate that our findings would help opening a new window onto developing the optimal pain treatment for the elderly.

Dependence of Hardness Change on Microstructure during Isothermal Aging in Mg-Al Alloy (Mg-Al 합금에서 등온 시효 중 경도 변화의 미세조직 의존성)

  • Han, Jin-Gu;Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.32 no.6
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    • pp.249-255
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    • 2019
  • This study is intended to clarify the main microstructural factors that contribute to an increase of hardness during isothermal aging in Mg-Al alloy. For this work, Mg-9.3%Al alloy specimens were solution-treated at 688 K for 24 h followed by water quenching, and then aged at 473 K for up to 24 h. The aging at 473 K yielded nodular discontinuous precipitates (DPs) with (${\alpha}+{\beta}$) lamellar morphology at the grain boundaries, and the volume fraction of DPs increased from 0% to ~30% with increasing aging time up to 12 h. For the aging times longer than 12 h, further formation of DPs was substantially inhibited owing to the occurrence of significant continuous precipitation within the ${\alpha}-(Mg)$ matrix, and the density of continuous precipitates (CPs) becomes greater with increasing aging time. Hardness of the specimen was steadily increased with aging time up to 24 h. Microstructural examination on the aged specimens revealed that the increased overall hardness at the early stage of aging is associated with the increased volume fraction of DPs, but at the later stage of aging, where the amount of DPs was hardly changed, the increased hardness of the ${\alpha}-(Mg)$ matrix in response to the higher density of CPs within the matrix, plays a key role in increasing the overall hardness value.

Effect of Thermal Cycle and Aging Heat Treatment on Transformation Characteristics of Cu-Zn-Al Shape Memory Alloys (Cu-Zn-Al계 형상기억합금의 변태특성에 미치는 열 Cycle 및 시효열처리의 영향)

  • Park, Pyeongyeol;Kim, Ickjun;Park, Seyun;Kim, Inbae;Park, Ikmin
    • Journal of the Korean Society for Heat Treatment
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    • v.2 no.4
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    • pp.47-55
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    • 1989
  • The effects of thermal cycle, aging heat treatment and Boron addition on the phase transformation characteristics and mechanical properties of the shape memory alloys of Cu-Zn-Al system, which was designed to operate about $80^{\circ}C$ by this research group, were studied. From the view point of the effects of thermal cycle on the phase transformation temperature change, it was found that up to 100 cycles Ms and Af points increased by $3-7^{\circ}C$ and Mf decreased a little bit and after that all of them were remain constant, and As point was not affected. All of the phase transformation temperatures were decreased $5-7^{\circ}C$ by aging heat treatment, at $140^{\circ}C$ for 24h however the effects of thermal cycle on aged alloys were same as on unaged alloys. As the thermal cycle increased the shape memory ability decreased a little up to 20 cycles, but above that it kept almost same ability. By Boron addition, grain size was refined from $1500{\mu}m$ to about $330{\mu}m$ and the hardness, fatigue property were improved but shape memory ability was lowered.

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Evolution of Microstructure and Mechanical Properties of Porous Al Alloy Under Various Heat Treatment (열처리에 따른 다공성 알루미늄 합금 재료의 미세구조와 기계적 성질 변화)

  • 류관무;권영재;김준규;조원승;조남희;황진명;유연철
    • Transactions of Materials Processing
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    • v.12 no.6
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    • pp.588-596
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    • 2003
  • The relationships between evolution of microstructure and mechanical properties of porous Al-3Si-2Mg-2Cu alloy after the foaming and various heat treating were investigated. The foamed alloy having various densities were manufactured by powder compact foaming and heat treated. Then compression test was performed with deformation rate of 0.5/s. The ultimate compression strength was not changed after solution heat treatment but the flow curve after ultimate strength showed very smooth and uniform plateau region. This change of flow curve means that the deformation mechanism is altered from brittle fracture to ductile deformation and the energy absorption property of Al foam is dramatically improved. The improvement of energy absorption without any detriment of mechanical properties is due to that the very brittle precipitation like Al-Cu and Al-Mg was uniformly dissolved in Al matrix after solution heat treatment. And various mechanical properties of Al alloy porous material were improved by 40% with aging of $200^{\circ}C$ and 50min. These improvements are ascribe to the various fine precipitates like $\Omega$ and $\theta$'.

Wire electrical discharge machining of titanium alloy according to the heat treatment conditions (열처리 조건에 따른 티타늄합금의 와이어 방전가공)

  • 김종업;왕덕현;김원일
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.930-933
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    • 2001
  • Titanium Alloys used in this experiment has an good corrosion resistance and specific strength, and is the new material developed for medical supplies living goods. In this study the rolled titanium alloy is done by annealing, solution heat-treatment and aging and then is worked by wire EDM. With changing the process conditions, the process properties of surface hardness, surface roughness, shape of process surface and the analysis of ingredients are measured through experiment repeating main cut and finish cut. It is confirmed to gain good measure values as increasing the number of processing of wire EDM. In this experiment the phenomena of processing is studied and the appropriate process condition is proposed.

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Microstructure and Mechanical Properties of Strip Casted Ag-27%Cu-25%Zn-3%Sn Brazing Alloy (브레이징용 Ag-27%Cu-25%Zn-3%Sn 박판 주조 스트립의 미세조직 및 기계적 특성 연구)

  • Kim, S.J.;Kim, M.C.;Lee, K.A.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.313-316
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    • 2008
  • This work sought to examine the suitability of twin roll strip casting for Ag-27%Cu-25%Zn-3%Sn brazing alloy (BAg-7A) and to investigate the mechanical properties and microstructure of the strip. The effect of aging heat treatment on the properties was also studied,. This new manufacturing process has applications in the production of the brazing alloy. XRD and microstructural analysis of the Ag-27%Cu-25%Zn-3%Sn strip represented eutectic microstructure of a Cu-rich phase and a Ag-rich matrix regardless of heat treatment. The results of mechanical tests showed tensile strength of 470MPa, a significant enhancement, and an 18% elongation of the twin roll casted strip, due mainly to the solid solution strengthening of Zn atoms (${\sim}20%$) in the Cu-rich phases. Tensile results showed gradually decreasing strengths and increasing elongation with aging heat treatment. Microstructural evolution and fractography were also investigated and related to the mechanical properties.

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