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Al-Mg-Si 합금에서 Cu 첨가와 자연시효 열처리가 열확산도에 미치는 영향
김유미 ( Yu-mi Kim ),최세원 ( Se-weon Choi ) 한국주조공학회 2021 한국주조공학회지 Vol.41 No.6
본 연구는 Al-Mg-Si 합금에서 Cu가 첨가 후 자연시효와 인공시효에 따른 제2상 석출 반응이 합금의 열확산도 및 경도에 미치는 영향을 연구하였다. 연구에 사용된 Al-0.4Mg-0.2Si 합금과 Cu를 0.6 wt%, 1.0wt% 추가한 Al-Mg-Si-Cu 합금을 각각 중력 주조로 제작하고 열확산도 경도를 측정하고 석출 반응을 확인하기 위해 열량 분석을 실시 하였다. Al-Mg-Si 합금에 첨가된 Cu는 Q′상 및 θ′상과 같은 강화상 형성에 참여하여 합금의 경도와 고온 열확산도를 향상시켰다. 한편, 자연시효 시간 증가는 Al-Mg-Si-Cu 합금의 열확산도에는 큰 영향을 미치지 않았으나, 경도를 하락시키는 것으로 확인되었다. To confirm effects of natural and artificial aging of precipitate on thermal diffusivity and hardness, the studied Al-Mg-Si alloy were manufactured by gravity casting method with 0.6 wt% and 1.0 wt% additional Cu element. The samples were used for measuring thermal diffusivity and hardness. The addition of Cu, promoted by intermediates such as Q″and θ″ phases, contributing to the improvement of hardness and high-temperature thermal diffusivity. The natural aging decreased the hardness of the Al-Mg-Si-Cu alloys with increasing time, but did not affect the thermal diffusivity.
차귀준,윤한기 東義大學校産業技術開發硏究所 1993 産業技術硏究誌 Vol.7 No.-
Effects of an accelerated iso-thermal aging (375˚x 66 days) and a prestressing on the elastic-plastic fracture toughness are examined for the unclear reactor pressure vessel steel, A533B-1, The elastic-plastic fracture toughness tests were conducted at the room temperature or 300˚C. In the test temperature, J₁c decreases due to above effects. However, if the results are interpreted in terms of total J-integral which accounts for J due to pre-loading, they have no effect. So, the main reason for decreasing J₁c should be attributed to the pre-loading. Also, they have no effect on the tangent of the R-curve.
제하 컴플라이언스법에 의한 SA533B강의 J<SUB>IC</SUB> 및 J-R 곡선에 미치는 열시효 영향
윤한기(Han-Ki Yoon),차귀준(Gee-Jun Cha) 한국해양공학회 1994 韓國海洋工學會誌 Vol.8 No.2
Effect of an accelerated iso-thermal aging (375℃×66days, 375℃×200days) on elastic-plastic fracture resistance curve were examined in SA533B low alloy steel. Fracture toughness test are conducted by unloading compliance method at room temperature. But the apparent negative crack growth phenomenon, usually arise in partial unloading compliance test. The phenomenon of negative crack growth may be eliminated by the offset technique. There is no effect of aging on J<SUB>IC</SUB> and dJ/da in iso-thermal aged (375℃×66 days) specimen, but there is very little effect in iso-thermal aged (375℃×200 days) specimen.
질소처리된 슈퍼오스테나이트 스테인리스강의 시효손상 평가
권일현(Il-Hyun Kwon),이송인(Song-In Lee),백승세(Seung-Se Baek),Y. Iino,유효선(Hyo-Sun Yu) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
To ensure the structural integrity and design life-time of the superaustenitic stainless steel containing 0.17wt% N and 5.5wt% Mo induced by artificially thermal aging treatment, material damage evaluation of the superaustenitic stainless steel was conducted by small punch (SP) and electrochemical polarization technique. The material damage in high-temperature and short-time aged material was higher than that in low-temperature and long-time aged material. A reasonable agreement was found between the results obtained from small punch and electrochemical polarization tests, depending on SP energy and the current density corresponding to the passivation film formation.
주조 오스테나이트 스테인리스강의 열취화 활성화에너지 분석
이경근(Gyeong-Geun Lee),홍석민(Suk-Min Hong),김지수(Ji-Su Kim),안동현(Dong-Hyun Ahn),김종민(Jong-Min Kim) 한국압력기기공학회 2024 한국압력기기공학회 논문집 Vol.20 No.1
Cast austenitic stainless steels (CASS) and austenitic stainless steel weldments with a ferrite-austenite duplex structure are widely used in nuclear power plants, incorporating ferrite phase to enhance strength, stress relief, and corrosion resistance. Thermal aging at 290-325°C can induce embrittlement, primarily due to spinodal decomposition and G-phase precipitation in the ferrite phase. This study evaluates the effects of thermal aging by collecting and analyzing various mechanical properties, such as Charpy impact energy, ferrite microhardness, and tensile strength, from various literature sources. Different model expressions, including hyperbolic tangent and phase transformation equations, are applied to calculate activation energy (Q) of room-temperature impact energies, and the results are compared. Additionally, predictive models for Q based on material composition are evaluated, and the potential of machine learning techniques for improving prediction accuracy is explored. The study also examines the use of ferrite microhardness and tensile strength in calculating Q and assessing thermal embrittlement. The findings provide insights for developing advanced prediction models for the thermal embrittlement behavior of CASS and the weldments of austenitic steels, contributing to the safety and reliability of nuclear power plant components.
Alloy 600의 PWSCC에 미치는 열적 시효 및 삼축 응력의 영향
유승창(Seung Chang Yoo),김종성(Jong Sung Kim),황일순(Il Soon Hwang),김지현(Ji Hyun Kim) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
In this study, the effects of triaxial stress was investigated in terms of primary water stress corrosion susceptibility. Thermally aged Alloy 600 specimens were prepared via accelerated heat treatment at 400 ℃ which is one of the highest temperature which will not cause the formation of excessive carbides or precipitates which will not be formed at nuclear power plant primary circuit environment. Triaxial stress was then applied by making round notch at the surface of round tensile specimen. The crack initiation time ere measured in-situ by direct current potential drop method during slow strain rate test at primary water condition. At the notched specimen, cracks were mainly observed at the region where shear stress is focused. Also, the stair shape of fracture surface was observed, which might cause by enhanced localized plasticity and multiple number of activated slip system under triaxial stress state.
가동 이력 화력 P91강의 재료거동 특성 시험 및 분석
이형연(Hyeong-Yeon Lee),김우곤(Woo-Gon Kim),어재혁(Jaehyuk Eoh) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12
In this study, the influence of service exposure on yield strength, tensile strength, fracture toughness and creep strength behavior for Mod.9Cr-1Mo (ASME Grade 91; P91) steel has been investigated with a number relevant material tests and analyses. The material properties of the ferritic-martensitic heat resistant material of P91 steel at ultra-supercritical (USC) thermal power plants are affected by long-term operation at high temperature in creep range as operating time is accumulated. Service exposed P91 steel materials sampled from a piping system of a domestic USC plant with accumulated operation time of 73,716 hours were used for material tests. The test results of the service exposed material specimens were compared with those of the virgin P91 steel specimens in terms of a number material properties. In addition, those test data were compared with the material properties of ASME code and RCC-MRx code. Quantification of conservatisms for the material properties in the design codes have been conducted based on the comparisons of those from virgin and service exposed material specimens.