• 제목/요약/키워드: aging treatment

검색결과 1,525건 처리시간 0.024초

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

  • 김상미;우기도;김지영;김상혁;박상훈;강황진;박찬성
    • 한국주조공학회지
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    • 제31권5호
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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.

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

  • 홍영준;김순호;강민철;김인배
    • 열처리공학회지
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    • 제6권3호
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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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5083 Al합금 용접재의 조직 및 저온 인장성질메 미치는 시효처리의 영향 (Effect of Aging Treatment on the Microstructure and Low Temperature Tensile Properties in 5083 Aluminum Alloy Weldments)

  • 이태청;이해우;주동원;이준희;성장현
    • 열처리공학회지
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    • 제13권1호
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    • pp.1-9
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    • 2000
  • The microstructural characteristics and low temperature tensile properties between $25^{\circ}C$ and $-196^{\circ}C$ for as-welded and age hardened specimen by using Al 5083-H321 for base metal, 5083-5356 and 5083-4043 weldments have been investigated. The hardness of 5083-5356 weldment decreases with aging treatment, whereas the weld region of 5083-4043 weldment shows remarkable increase in hardness after aging due to the precipitation of fine Si particle at the grain boundaries and interiors. Low temperature tensile properties of 5083 AI base metal, 5083-5356 and 5083-4043 weldments appear to be the increment of tensile strengths and elongations at the room temperature and $-196^{\circ}C$, while the decrement of tensile properties around $-50^{\circ}C$ is shown. Through the observation of fine serration to fracture in the stress-strain curve and tensile fractography, the increment of localized deformation leading to promote the neck initiation and the increment of the dimple size cause to decrease in tensile strengths and elongations around $-50^{\circ}C$. For the tensile specimen of the 5083 base metal, 5083-5356 and 5083-4043 weldments, the reason to increase in elongation after solution and aging treatment is the diminishment of fine pit, the resolution of Mg into the matrix and the spheridization of the eutectic Si.

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극저온 열처리 공정이 6061 알루미늄 합금의 잔류응력과 인장특성에 미치는 영향 (Effects of Cryogenic Treatment on Residual Stress and Tensile Properties for 6061 Al Alloy)

  • 박기정;고대훈;김병민;임학진;이정민;조영래
    • 대한금속재료학회지
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    • 제49권1호
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    • pp.9-16
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    • 2011
  • To develop a 6061 aluminum alloy with low residual stress and high tensile strength, a cryogenic treatment process was investigated. Compared to the conventional heat treatment process for precipitation hardening with artificial aging, the cryogenic treatment process has two additional steps. The first step is cryogenic quenching of the sample into liquid nitrogen, the second step is up-hill quenching of the sample into boiling water. The residual stress for the sample was measured by the $sin^2{\psi}$ method with X-ray diffraction. The 6061 aluminum alloy sample showed 67% relief in stress at the cryogenic treatment process with artificial aging at $175^{\circ}C$. From this study, it was found that the optimum cryogenic treatment process for a sample with low residual stress and high tensile strength is relatively low cooling speed in the cryogenic quenching step and a very high heating speed in the up-hill quenching step.

열분석법에 의한 Al-2.1Li-2.9Cu합금의 석출현상(II) - 시효거동 - (The Precipitation Phenomena of Al-2.1Li-2.9Cu alloy by Differential Scanning Calorimetry(III) - Aging behaviors -)

  • 박태원
    • 열처리공학회지
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    • 제10권1호
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    • pp.63-70
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    • 1997
  • A study was performed to examine the aging behaviors of Al-2.1Li-2.9Cu alloy by differential scanning calorimetry and transmission electron microscopy. DSC measurements were conducted over the temperature range of $25{\sim}550^{\circ}C$ at a heating rate of $5^{\circ}C$/min. for the specimens aged at 130, 160, $190^{\circ}C$ and $220^{\circ}C$ for various times after solution treatment at $540^{\circ}C$ for 30 minutes. The peaks due to the formation of G.P.zone were not detected in the specimens aged at 130 and $160^{\circ}C$, but those at 190 and $220^{\circ}C$ appeared in DSC curves. The heat absorption due to the dissolution of ${\delta}^{\prime}$ phase was increased with increasing aging time at $130^{\circ}C$ aging. In contrast, those values for the specimens aged at 160 and $190^{\circ}C$ were initially increased and inversely decreased at the transition time of 72 and 1 hour, respectively. The heat evolution due to the formation of $T_1$ phase was nearly unchanged at $130^{\circ}C$ aging, but at $160^{\circ}C$ and $190^{\circ}C$ aging, drastically decreased after the transition time. It can be considered that the increase of $T_1$ phase results in the decrease of ${\delta}^{\prime}$ phase when aging time is longer than the transition time. The hardness of the specimen aged at $190^{\circ}C$ is initially higher compared with that at $160^{\circ}C$, however, the peak hardness shows the lower value than that at $160^{\circ}C$.

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Ca과 Y 복합 첨가가 AZ91 마그네슘 압출재의 시효 거동에 미치는 영향 (Effect of Combined Addition of Ca and Y on Aging Behavior of Extruded AZ91 Magnesium Alloy)

  • 김현지;김영민;배준호;박성혁
    • 소성∙가공
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    • 제31권3호
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    • pp.160-166
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    • 2022
  • The purpose of this study is to investigate the effects of combined addition of Ca and Y on the precipitation and age-hardening behavior of an extruded AZ91 alloy by conducting the aging treatment at 200 ℃ for hot-extruded AZ91 and AZ91-0.3Ca-0.2Y alloys. In the AZ91 alloy, many Mg17Al12 discontinuous precipitate (DP) bands formed during air cooling immediately after extrusion are present, whereas in the AZ91-0.3Ca-0.2Y alloy, a few DP bands and numerous Al2Y, Al8Mn4Y, and Al2Ca phase particles are distributed along the extrusion direction. The peak-aging time of the AZ91-0.3Ca-0.2Y alloy is 16 hours, twice that of the AZ91 alloy. Although both alloys have similar hardness before aging treatment, the hardness after peak-aging treatment (i.e., peak hardness) of the AZ91-0.3Ca-0.2Y alloy is higher than that of the AZ91 alloy, as 93.1 and 88.7 Hv, respectively. The microstructures of both peak-aged alloys comprise DPs and continuous precipitates (CPs). However, the peak-aged AZ91-0.3Ca-0.2Y alloy has a smaller amount of DPs and a larger amount of CPs than the peak-aged AZ91 alloy. Additionally, the inter-particle spacings of DPs and CPs in the former are significantly narrower than those in the latter. These results demonstrate that the addition of small amounts of Ca and Y to a commercial AZ91 alloy considerably affects the formation rate, size, and amount of CPs and DPs during aging and resultant age-hardening behavior.

Corni Fructus attenuates testosterone-induced benign prostatic hyperplasia by suppressing 5α-reductase and androgen receptor expression in rats

  • Hwangbo, Hyun;Kwon, Da He;Choi, Eun Ok;Kim, Min Yeong;Ahn, Kyu Im;Ji, Seon Yeong;Kim, Jong Sik;Kim, Kyung-Il;Park, No-Jin;Kim, Bum Hoi;Kim, Gi-Young;Hong, Su-Hyun;Park, Cheol;Jeong, Ji-Suk;Choi, Yung Hyun
    • Nutrition Research and Practice
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    • 제12권5호
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    • pp.378-386
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    • 2018
  • BACKGROUND/OBJECTIVES: Benign prostatic hypertrophy (BPH) is a major cause of abnormal overgrowth of the prostate mainly in the elderly. Corni Fructus has been reported to be effective in the prevention and treatment of various diseases because of its strong antioxidant effect, but its efficacy against BPH is not yet known. This study was designed to evaluate the therapeutic efficacy of Corni Fructus water extract (CF) in testosterone-induced BPH rats. MATERIALS/METHODS: To induce BPH, rats were intraperitoneal injected with testosterone propionate (TP). Rats in the treatment group were orally administered with CF with TP injection, and finasteride, which is a selective inhibitor of $5{\alpha}$-reductase type 2, was used as a positive control. RESULTS: Our results showed that the increased prostate weight and histopathological changes in BPH model rats were suppressed by CF treatment. CF, similar to the finasteride-treated group, decreased the levels of testosterone and dihydrotestosterone by TP treatment in the serum, and it also reduced $5{\alpha}$-reductase expression and concentration in prostate tissue and serum, respectively. In addition, CF significantly blocked the expression of the androgen receptor (AR), AR co-activators, and proliferating cell nuclear antigen in BPH rats, and this blocking was associated with a decrease in prostate-specific antigen levels in serum and prostate tissue. CONCLUSIONS: These results suggest that CF may weaken the BPH status through the inactivation of at least $5{\alpha}$-reductase and AR activity and may be useful for the clinical treatment of BPH.

꼬마선충에서 메밀 추출물에 의한 산화성 스트레스 저항성 증가 및 수명 연장 효과 (Buckwheat Extract Increases Resistance to Oxidative Stress and Lifespan in Caenorhabditis elegans)

  • 김철규;박상규
    • 한국약용작물학회지
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    • 제21권1호
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    • pp.1-6
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    • 2013
  • Buckwheat (Fagopyrum esculentum) has been known for having strong anti-oxidant, anti-mutagenic, and anti-carcinogenic activities. The free radical theory of aging, also known as the oxidative stress theory of aging, claims that cellular oxidative damage accumulated with time is a major causal factor of aging. In the present study, we investigated the effect of buckwheat extracts on resistance to oxidative stress and aging using Caenorhabditis elegans as a model system. Survival under an oxidative-stress condition induced by paraquat increased markedly following 500mg/L buckwheat extracts treatment, suggesting lower cellular oxidative damage by buckwheat extracts. A lifespan assay also revealed that treatment of buckwheat extracts significantly extended both the mean and maximum lifespan in C. elegans. Interestingly, this lifespan-extension by buckwheat extracts was not accompanied by reduced fertility. These findings suggest that buckwheat extracts can confer longevity phenotype to C. elegans through its strong anti-oxidant activity and support the aging theory which emphasizes a pivotal role of oxidative stress during aging.

열처리조건에 따른 Cu-Ni-Si-Sn-Fe-P 석출경화형 동합금계의 물성변화 특성 (Mechanical and Physical Property Changes of Cu-Ni-Si-Sn-Fe-P Copper Alloy System According to the Heat Treatment Conditions)

  • 김승호;염영진
    • 열처리공학회지
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    • 제26권5호
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    • pp.225-232
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    • 2013
  • The influence of aging treatment, addition elements and rolling reduction ratio on the microstructure, mechanical, electrical and bendability properties of Cu-Ni-Si-P-x (x = Fe, Sn, Zn) alloys for connector material application was investigated. SEM/EDS analysis exhibited that Ni2-Si precipitates with a size of 20~100 nm were distributed in grains. Fe, Sn, Zn elemnets in Cu-Ni-Si-P alloy imporved the mechanical strength but it was not favor in increasing of electrical conductivity. As higher final rolling reduction ratio, the strength and electrical conductivity is increased after aging treatment, but it indicated excellent bendability. Especially, Cu-2Ni-0.4Si-0.5Sn-0.1Fe-0.03P alloy show the tensile strength value of 700MPa and the electrical conductivity was observed to reach a maximum of 40%IACS. It is optimal for lead frame and connector.

노인성 음성에 대한 최신 연구동향 (Current Researches on Vocal Fold Aging)

  • 임재열
    • 대한후두음성언어의학회지
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    • 제25권1호
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    • pp.24-26
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    • 2014
  • Aging causes a variety of changes in the structure of the vocal fold (VF), resulting in aging-induced dysphonia (presbyphonia). Several studies have investigated the structure of the VF of elderly people from autopsy as well as animal studies. There is an increasing evidence on correlation of structural changes of VF with deteriorated voice in elderly. Although the cellular mechanisms of aging VF have only partially been elucidated, there are many recent advances in biological treatment on aging VF using bioactive molecules such as growth factors. In this study, I'd like to address aging-related structural, biological, and physiological changes in previous literature about human and rodent aging VFs, to provide further insight into the mechanisms responsible for presbyphonia and to translate the basic researches for future clinical trials.

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