• 열처리공학회지
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• 제32권2호
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• pp.57-60
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• 2019

The impact of two-step treatment on the mechanical properties of the 6061 Al alloy was investigated by testing the hardness and electrical conductance values. After two-step aging treatment, the hardness and electrical conductivity of the alloy was increased, and if the first aging treatment temperature was lower than the secondary aging treatment temperature, both the hardness and the electrical conductivity were not increased. The higher the temperature of the first aging treatment, the higher the hardness. The temperature of the first aging treatment is $175^{\circ}C$, $150^{\circ}C$, $120^{\circ}C$, and the second is $175^{\circ}C$ and $120^{\circ}C$.

• Journal of Welding and Joining
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• 제21권3호
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• pp.78-84
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• 2003

The changes of microstructure and hardness of TLP bonds of directionally solidified Ni base superalloy, GTD-111, with variation of homogenizing and aging treatment were investigated. The specimens were bonded at 1403K for 7.2ks using different insert metals such as MBF-50, MBF-80 and MBF-90 and they were homogenized at 1393K with various holding time. At center of bonded interlayer homogenized for hold time 30h, the contents of aluminum and titanium were approximately 90% and 95% of base metal, respectively. In this study, aging was performed at three different kinds : one step aging ; 1113K $\times$ 16h, two step aging ; 1113K $\times$ 10h ⇒ 1103K $\times$ 10h, three step aging ; 1113K $\times$ 10h ⇒ 1103K $\times$ 8h ⇒ 922K $\times$ 24h. ${\gamma}$' volume fraction and hardness of joints were high in the sequence of one step, two step and three step aging, whereas ${\gamma}$' volume fraction and hardness of joints obtained by three step aging treatment were higher than those of raw material. Tensile properties of joints bonded with MBF-80 and MBF-90, homogenized at 1393K for 30h and then three step aged became excellent than those of raw material, however, joint bonded with MBF-50 was poor.

• 한국재료학회지
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• 제10권7호
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• pp.493-498
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• 2000

7050 AI합금을 RRA 처리하였을 때 경도, 전기전도도 및 미세조직의 변화를 조사하였다. 120도씨에서 24시간 동안 1차 시효처리한 후 175도씨에서 2차 퇴화처리하였을 때 경도값의 변화는 초기에 감소하다가 피크 경도를 보인 다음 다시 감소하였으며, 3차 재시효처리재가 2차 시효처리재 보다 큰 경도값을 나타내었다. 2차 퇴화처리시 초기 경도 감소는 T6의 주 강화상인 GP zone의 부분적인 분해에 의한 것이며, 3차 재시효 처리하였을 때 강화상은 GP zone과 파이상이었다. 120도씨에서 24시간 동안 1차 시효처리한 후 175도씨에서 2차 퇴화처리하였을 때 전기전도도 변화는 퇴화 쵤부터 연속적으로 증가혀였으며, 3차 재시효처리에 의해 2차 퇴화처리시 보다 %IACS가 0.5 ~ 2.7 증가하였다. 3단시효에 의해 T6정도의 강도를 유지하면서 38%IACS값 이상의 전기전도도를 얻을 수 있는 최적 퇴화처리 조건은 $175^{\circ}C$ 50분이었다. 이는 퇴화처리 경도곡선의 극소점 또는 극대점과 무관하며 오히려 약간 과시효 조건이다.

• 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.

• 한국식품저장유통학회지
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• 제23권3호
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• pp.301-309
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• 2016

미숙과의 가공법 제안 및 기능성 규명을 위한 기초 연구의 일환으로 반시 미숙과를 7 step으로 나누어 열처리 숙성하면서 이화학적 특성 및 항산화 활성의 변화를 분석하였다. 반시 미숙과는 숙성됨에 따라 수분함량과 pH는 점차 감소하고, 산도는 증가하는 경향이었다. 숙성이 진행됨에 따라 갈변이 유도되면서 step 3까지 적색도는 급격히 증가하였으며, 황색도는 큰 폭으로 감소하였다. 반시의 탄력성, 씹힘성과 점착성의 경우에는 step 2~3에서 변화한 후에는 유의적인 차이를 보이지 않았다. 숙성 중 반시 미숙과의 fructose의 함량은 감소한데 반해 glucose 함량은 미량 증가하였다. 페놀성 화합물은 gallic acid와 homogentisic acid, 2종이 검출되었는데 이들 화합물은 step 2까지는 검출되지 않았으나, step 3부터 숙성단계가 지남에 따라 함량이 증가하였다. 이와 상반되게 탄닌 함량은 step 1에서 가장 높게 측정되었고 step 2에서 급감하였다. 숙성 단계별 반시 미숙과 물 추출물의 DPPH와 ABTS 라디칼 소거능 및 FRAP법에 따른 항산화 활성은 시료의 농도에 비례하여 유의적으로 증가하였으나, 숙성이 진행될수록 오히려 낮아졌다.

• 수산해양기술연구
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• 제20권1호
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• pp.23-29
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• 1984

고역알루미늄합금의 파괴특성에 미치는 시효열처리의 영향에 대하여 검토한 결과는 다음과 같다. 1. 현미경 조직의 관찰결과 $190^{\circ}C,$ 12hr로 시효열처리한 것이 시효강화된 양호한 조직과 미세한 석출분포를 나타내고 있음을 알 수 있었다. 2. 계단식시효열처리에 의하여 정상시효열처리보다 시효시간을 반정도로 단축시킬 수 있었고, 이들 조직도 유사하였다. 3. 인장파단면의 SEM 전자현미경 사진관찰결과는 $190^{\circ}C,$ 12hr으로 시효열처리한 것은 딤플형 입계 및 입내연성파괴를 나타내나, 이를 제외한 대부분은 시효열처리 시간과 온도에는 관계없이 입계연성파괴인 것이 관찰되었다.

• 한국재료학회지
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• 제9권7호
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• pp.695-700
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• 1999

7050 Al합금의 응력부식저항성에 미치는 2단 시효처리의 영향을 미세조직관찰, 전기전도도시험 및 SCF값을 평가함으로써 조사하였다. 최대 경도 이상 과시효에 의해 주 강화상인 η'상이 η상으로 변태되었고, 입내 및 입계에 존재하는 η상의 크기와 간격이 커졌으며 그 결과 응력부식저항성이 증대되었다. 2차 시효시간의 증가에 따라 전기전도도값은 증가되었으나 항복강도의 감소로 인하여 SCF값은 감소되었는데, 이러한 결과는 응력부식저항성의 증가를 의미한다. AMS 4107규격을 기준으로 하였을 때 7050 Al합금 단조재의 적정시효조건은 1차시효가 12$0^{\circ}C$에서 6시간, 2차시효는 $175^{\circ}C$에서 12시간이었다.

• 한국재료학회지
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• 제15권12호
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• pp.773-779
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• 2005

Properties of Ni-base superalloys of Nimonic 80A alloy system were investigated by the observation of microstructures, precipitates ana hardness as a function of the chemical compositions ana the paths of heat treatment. The higher hardness values showed, the higher Ti/Al ratio among high compositions of Cr and Co element. The lower (Ti+Al) and Fe contents decreased in the same Ti/Al ratio, the higher hardness values showed. This results are considered that coherent deformation was increased with increasing Ti/Al ratio. Hardness showed higher value when Cr contents was $18 wt\%$ less than $21wt\%Cr$. In $3.15 wt\%$Co alloy, $\gamma'$ phase was very fine as around 50nm and, its volume fraction and hardness showed the highest value by 2step-aging treatment.

• 열처리공학회지
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• 제8권4호
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• pp.333-339
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• 1995

The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

• 대한두경부종양학회지
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• 제33권2호
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• pp.1-8
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• 2017

Cancer is the disease of aging and Korea is one of the fastest aging country in the world. Older patients have decreased organ function and stress tolerance, therefore are at high risk of functional decline and developing complication from cancer and cancer treatment. Before beginning cancer treatment, it is important to assess patients' life expectancy, whether the patient is likely to die of cancer or of other comorbidity, and also the risks with cancer treatment. In order to estimate patient's physiologic age, it is recommended to perform geriatric assessment and implement appropriate geriatric intervention together with meticulous supportive care, when planning cancer treatment for older patients. In a resource limited country such as Korea, two step approach of applying screening tool followed by geriatric assessment can be more efficient. Geriatric assessment is used to predict toxicity from cancer treatment such as surgery, radiotherapy, and chemotherapy, predict survival, and also to aid treatment decision. Number of randomized trials are ongoing to compare usual care versus oncogeriatric care, and with these results we expect to improve outcome of older patients with cancer.