• Title/Summary/Keyword: Transformation Heat

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Effect of Phase Transformation Behavior of Electroless Nickel Plating Layer on Corrosion and Cavitation-Erosion with Heat Treatment (열처리에 따른 무전해 니켈 도금 층의 상변태 거동이 부식과 캐비테이션 침식에 미치는 영향)

  • Il-Cho Park;Seong-Jong Kim
    • Corrosion Science and Technology
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    • v.23 no.1
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    • pp.64-71
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    • 2024
  • The objective of this study was to investigate corrosion and cavitation-erosion characteristics of the electroless nickel plating layer with heat treatment. The crystallization temperature of the electroless nickel plating layer was about 410 ℃. The phase transformation energy was confirmed to be 12.66 J/g. With increasing heat treatment temperature, the amorphous electroless nickel plating layer gradually changed to crystalline Ni and Ni3P. At the same time, the crystal grain size was also increased. Additionally, when heat treatment was performed at a temperature above 400 ℃, NiO phase was observed due to oxidation phenomenon. As a result of the electrochemical polarization experiment, the corrosion resistance of the heat-treated electroless nickel plating layers was superior to that of the as-deposited plating layer. This was because crystal grains became larger and grain boundaries decreased during heat treatment. The cavitation-erosion resistance of heat-treated plating layers tended to be superior to that of as-deposited plating layers due to increased microhardness.

Study on predictive model and mechanism analysis for martensite transformation temperatures through explainable artificial intelligence (설명가능한 인공지능을 통한 마르텐사이트 변태 온도 예측 모델 및 거동 분석 연구)

  • Junhyub Jeon;Seung Bae Son;Jae-Gil Jung;Seok-Jae Lee
    • Journal of the Korean Society for Heat Treatment
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    • v.37 no.3
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    • pp.103-113
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    • 2024
  • Martensite volume fraction significantly affects the mechanical properties of alloy steels. Martensite start temperature (Ms), transformation temperature for martensite 50 vol.% (M50), and transformation temperature for martensite 90 vol.% (M90) are important transformation temperatures to control the martensite phase fraction. Several researchers proposed empirical equations and machine learning models to predict the Ms temperature. These numerical approaches can easily predict the Ms temperature without additional experiment and cost. However, to control martensite phase fraction more precisely, we need to reduce prediction error of the Ms model and propose prediction models for other martensite transformation temperatures (M50, M90). In the present study, machine learning model was applied to suggest the predictive model for the Ms, M50, M90 temperatures. To explain prediction mechanisms and suggest feature importance on martensite transformation temperature of machine learning models, the explainable artificial intelligence (XAI) is employed. Random forest regression (RFR) showed the best performance for predicting the Ms, M50, M90 temperatures using different machine learning models. The feature importance was proposed and the prediction mechanisms were discussed by XAI.

Effect of Prior Deformation on the Martensitic Transformation Temperature(Ms) and Reversed Martensitic Transformation Temperature(As) in Fe-Ni Alloy (Fe-Ni합금(合金)의 마르텐사이트변태온도(變態溫度)(Ms)와 역변태온도(逆變態溫度)(As)에 미치는 소성가공(塑性加工)의 영향(影響))

  • Shon, In-Jin;Nam, Kee-Seok
    • Journal of the Korean Society for Heat Treatment
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    • v.3 no.4
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    • pp.41-52
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    • 1990
  • This research has been performed in order to investigate the effect of prior deformation on the Ms temperature and reversed As of Fe-Ni alloy. The Ms temperature rose with increment of strain to 30% but lowered over 50%. It can be analysed that martensitic transformation was promoted by partial dislocation in low strain, but suppressed by dislocation cell structures in high strain. The As temperature was substantially increased with higher deformation to 20% but slowly above 50%. It may be caused that as the transition bands formed by deformation constrained shear strain, therefore austenitic transformation was hindered.

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A Study on the Prediction Modeling of Phase Transformation in the CGHAZ of Structural Steel Weld (구조용강 용접부 CGHAZ의 상변태 예측 Modeling에 관한 연구)

  • 조일영;이경종;이창희
    • Journal of Welding and Joining
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    • v.16 no.3
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    • pp.74-84
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    • 1998
  • The microstructures of the HAZ (Heat Affected Zone) are generally different from the base metal due to rapid thermal cycle during welding process. Particuraly, CGHAZ (Coarsened Grain Heat Affected Zone) near the fusion line is the most concerned region in which many metallurgical and mechanical discontinuities have been normally generated. A computer program by the numerical formularization of phase transformation during cooling with different rates was developed to generate the CCT diagram, and to predict microstructural (phase) changes in the CGHAZ. In order to verify simulated results, isothermal and continuous cooling transformation experiments were conducted. The simulated and experimental results showed that the developed computer model could successfully predict the room temperature microstructural changes (changes in volume fraction of phases) under various welding conditions (heat input & cooling rate $(Δt_{8/5})$).

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An Analysis Finite Element for Elasto-Plastic Stresses Considerating Phase Transformation at the Quenching Process(II) -From Austenite to Martensite- (퀜칭과정에서 상변태를 고려한 탄소성 열응력의 유한요소 해석(II) -오오스테나이트에서 마르텐사이트로의 변태-)

  • Kim, O.S.;Song, G.H.;Koo, B.K.
    • Journal of the Korean Society for Heat Treatment
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    • v.8 no.1
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    • pp.12-23
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    • 1995
  • In this a set of constitutive equation relevant to the analysis of thermo-elasto-plastic materials with phase transformation during quenching process was presented on the basis of continuum thermo-dynamic. In calculating the transient thermal stresses, temperature between coolant and specimen(SM45C) surface was determined from the heat transfer coefficient. A calculation was made for specimen with 40mm in diameter quenched in coolant from $820^{\circ}C$ and the results are as follow. Stresses at starting point of transformation always show the maximum tensile value. Reverse of stresses takes place after completion of transformation of inner part at specimen.

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Driving Forces for γ→ε Martensitic Transformation of Fe-Mn Alloys (Fe-Mn 합금의 γ→ε 마르텐사이트변태에 필요한 구동력)

  • Lee, Young-Kook;Choi, Chong-Sool
    • Journal of the Korean Society for Heat Treatment
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    • v.9 no.4
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    • pp.243-251
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    • 1996
  • Dilatometric experiment and thermodynamic calculation have been performed to determine $M_s$, $A_s$ and driving forces for ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation of Fe-Mn alloys. The transformation temperatures($M_s$, $A_s$, $T_o) were decreased with increasing manganese content and were newly formulated as a function of manganese content. Driving force for ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation was increased from -75J/mole to -105J/mole with increasing manganese content from 15wt.% to 25wt.%. Transformation temperature hysteresis($A_s-M_s$) was also increased from 50K to 80K with increasing mangenese content from 15wt.% to 25wt.%. The small driving force(-75J/mole~-105J/mole) and small ${\Delta}T$(50K~80K) for ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation indicated that Fe-Mn alloys behave like thermoelastic martensitic alloys : We would like to call them semi-thermoelastic martensitic alloys.

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Phase Transformation Behavior on Aging Treatment in CuAINi Shape Memory Alloy (CuAINi 형상기억합금의 시효처리에 따른 상변태 거동)

  • Yang, G.S.;Kang, J.W.
    • Journal of the Korean Society for Heat Treatment
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    • v.6 no.4
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    • pp.213-222
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    • 1993
  • This research was performed to investigate the transformation behavior and shape memory effect of Cu-13.5Al-4.5Ni(wt%) alloy with various aging temperature and time. The results obtained in this study are as follows: Transformation temperature was very increased when aging temperature is at $250^{\circ}C$. The variation of transformation temperature in first reverse transformation cycle and second was very significant, but there was little difference in case of 2nd and 3rd. Transformation temperature at various aging temperature was increased with increasing of aging temperature and time. Microvickers hardness was increased with increasing of aging temperature and time. It was found that ${\alpha}$ and ${\gamma}_2$ phase were created by aging of long time at high temperature.

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Microstructures and Tensile Properties by Multi-step Isothermal Heat Treatment in Conventional TRIP Steel (상용 TRIP강의 다단 항온 변태 열처리에 따른 미세조직 및 인장 특성)

  • Kim, Kyeong-Won;Lee, Chang-Hoon;Kang, Jun-Yun;Lee, Tae-Ho;Cho, Kyung-Mox
    • Journal of the Korean Society for Heat Treatment
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    • v.29 no.3
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    • pp.103-108
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    • 2016
  • In recent years, TRIP steels which are composed of ferrite, bainite, and retained austenite have drawn much attention for automotive sheets due to excellent combination of strength and ductility. The effect of two-step isothermal heat treatment of bainitic transformation on microstructures, especially retained austenites and tensile properties in the conventional TRIP steel was investigated. A two-step isothermal heat treatment, in which 50% bainitic transformation occurred at high temperature, followed by bainitic transformation at low temperature, improves tensile properties, resulting from enhanced mechanical stability of retained austenite against external plastic deformation due to refinement of retained austenites, compared to single-step isothermal heat treatment.

Effects of Heat Inputs on Phase Transformation and Resistance to Intergranular Corrosion of F316 Austenitic Stainless Steel (F316 오스테나이트 스테인리스강의 상변태 및 입계부식저항성에 미치는 입열의 영향)

  • Jeong, Gyue-Seog;Lee, In-Sung;Kim, Soon-Tae
    • Corrosion Science and Technology
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    • v.19 no.3
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    • pp.146-155
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    • 2020
  • To elucidate the effect of heat inputs on phase transformation and resistance to intergranular corrosion of F316 austenitic stainless steel (ASS), thermodynamic calculations of each phase and time-temperature-transformation diagram were conducted using JMaPro simulation software, oxalic acid etch test, double-loop electrochemical potentiokinetic reactivation test (DL-EPR), field emission scanning electron microscopy with energy dispersive spectroscopy, and transmission electron microscopy analyses of Cr carbide (Cr23C6), austenite phase and ferrite phase. F316 ASS containing a relatively low C content of 0.043 wt% showed a slightly sensitized microstructure (acceptably dual structure) due to a small amount of Cr carbide precipitated at heat affected zone irrespective of heat inputs. Based on results of DL-EPR test, although heat input was increased, the ratio of Ir to Ia was only increased very slightly due to a slight sensitization. Therefore, heat inputs have little influences on resistance to intergranular corrosion of F316 austenitic stainless steel containing 0.043 wt% C.

A study on the development of the fin-tube heat exchanger pollution ratio evaluation algorithm using Image Processing and Affine Transformation (영상처리 및 어파인변환을 이용한 핀튜브 열교환기 오염율 평가 알고리즘 개발에 관한 연구)

  • Park, Sungmin;Jung, Myungin;Whang, Kwangil;Cho, Gyeongrae
    • Journal of the Korean Society of Visualization
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    • v.20 no.1
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    • pp.11-17
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    • 2022
  • Among the various factors that cause the performance decrease of heat exchangers used in many industries, flow path blocking is one of the important and serious factor. In order to solve this problem, proper maintenance and management of the heat exchanger is important and emphasized. In this study, we developed and algorithm that can quantitatively determine and diagnose the normal and blocked areas of fin-tube heat exchanger using pattern analysis, Gaussian Edge Detection, Image Processing and Affine Transformation techniques. The developed algorithms was applied to the actual heat exchanger and the performance was evaluated by comparing with the manual results. From these results, it was proved that the developed algorithm is effective in evaluating the pollution ratio of the fin-tube heat exchanger.