• 한국해양공학회지
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• 제20권1호
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• pp.1-6
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• 2006

The effects of microstructure on the damping capacity and tensile properties of 316L stainless steel were investigated. Increasing the degree of cold working, the volume fraction of $\varepsilon-martensite$ decreased after rising to maximum value at specific level of cold working, the volume fraction of d-martensite slowly increased and then dramatically increased from the point of decreasing $\varepsilon-martensite$ volume fraction. Increasing the degree of cold working, the behnvior of damping capacity is similar to that of the $\varepsilon-martensite$. After the damping capacity showing the maximum value at about $20\%$ of cold rolling, damping capacity was decreased with the volume fraction of $\varepsilon-martensite$. Tensile strength was proportional to the volume fraction of d-martensite, and elongation steeply decreased in the range low volume fraction of a'-martensite, then slowly decreased in range the above $10\%$ volume fraction of d-martensite. The damping capacity and elongation is strongly controlled by the volume fraction of $\varepsilon$ martensite with liner relationship. However, the effect of the volume fraction of d-martensite and austenite phase on the damping capacity was not observed. Tensile strength was governed by the volume fraction of d-martensite.

• 한국재료학회지
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• 제26권9호
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• pp.493-497
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• 2016

This study was carried out to investigate the effect of deformation induced martensite on the damping capacity of Fe-26Mn-4Co-2Al damping alloy. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite were formed by cold working, and; deformation induced martensite was formed with according to the specific direction and the surface relief. With an increasing degree of cold rolling, the volume fraction of ${\alpha}^{\prime}$-martensite increased rapidly, while the volume fraction of ${\varepsilon}$-martensite decreased after rising to a maximum value at a specific level of cold rolling. Damping capacity was increased, and then decreased with an increasing of the degree of cold rolling. Damping capacity was influenced greatly by the volume fraction of ${\varepsilon}$-martensite formed by cold working, but the effect of the volume fraction of ${\alpha}^{\prime}$-martensite have a actually on effect on the damping capacity.

• 열처리공학회지
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• 제16권4호
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• pp.211-215
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• 2003

In this work, a new way of measuring the volume fraction of e martensite in Fe-based alloys has been proposed. Since the specific volume of ${\varepsilon}$ martensite, depending on alloy composition, is smaller than that of austenite i.e ${\gamma}$ phase, volume expansion takes place during ${\varepsilon}{\rightarrow}{\gamma}$ reverse transformation. As the amount of the volume expansion is proportional to the product of specific volume difference times the volume fraction of ${\varepsilon}$ martensite, the volume fraction of ${\varepsilon}$ martensite can be calculated by measuring the volume expansion and the specific volume difference. Such a relationship was confirmed in Fe-21Mn and Fe-32Mn-6Si alloys which undergo ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation on cooling and by cold rolling, respectively. It was also found that the former has isotropic ${\varepsilon}$ martensite while the latter has anisotropic ${\varepsilon}$ martensite.

• 동력기계공학회지
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• 제20권6호
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• pp.46-50
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• 2016

This study was carried out to investigate the effect of cold working on the tensile strength of Fe-26Mn-4Co-2Al damping alloy. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite were formed by cold working, and martensite was formed with the specific direction and surface relief. With the increasing degree of cold rolling, volume fraction of ${\alpha}^{\prime}$-martensite was increased, whereas the volume fraction of ${\varepsilon}$-martensite was decreased after rising to maximum value at specific lever of cold rolling. Tensile strength was linearly increased with an increasing of degree of cold rolling. Tensile strength was strongly affected to the volume fraction of ${\varepsilon}$-martensite formed by cold working, but the effect of volume fraction of ${\varepsilon}$-martensite on the tensile strength was not observed.

• 한국재료학회지
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• 제29권3호
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• pp.160-166
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• 2019

This study investigates the effect of thermo-mechanical treatment on the damping capacity of the Fe-20Mn-12Cr-3Ni-3Si alloy with deformation induced martensite transformation. Dislocation, ${\alpha}^{\prime}$ and ${\varepsilon}-martensite$ are formed, and the grain size is refined by deformation and thermo-mechanical treatment. With an increasing number cycles in the thermo-mechanical treatment, the volume fraction of ${\varepsilon}-martensite$ increases and then decreases, whereas dislocation and ${\alpha}^{\prime}-martensite$ increases, and the grain size is refined. In thermo-mechanical treated specimens with five cycles, more than 10 % of the volume fraction of ${\varepsilon}-martensite$ and less than 3 % of the volume fraction of ${\alpha}^{\prime}-martensite$ are attained. Damping capacity decreases by thermo-mechanical treatment and with an increasing number of cycles of thermo-mechanical treatment, and this result shows an opposite tendency for general metal with deformation induced martensite transformation. The damping capacity of the thermo-mechanical treated damping alloy with deformation induced martensite transformation greatly affect the formation of dislocation, grain refining and ${\alpha}^{\prime}-martensite$ and then ${\varepsilon}-martensite$ formation by thermo-mechanical treatment.

• 열처리공학회지
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• 제15권6호
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• pp.255-259
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• 2002

Effect of martensite on the mechanical properties of austempered ductile cast iron was investigated after obtained the martensite by subzero treatment. Retained austenite was transformed to martensite by subzero treatment, and with decreasing subzero treatment temperature, volume fraction of martensite was increased. With increasing of the volume fraction of martensite, tensile strength was increased and elongation was decreased, ratio of increasing of strength and decreasing of elongation was higher in case of specimens with lot's of Cu contents. With increasing of the volume fraction of martensite, hardness slowly increased until only about 5% and it rapidly increased in a straight proportion when it is above 5%, while impact value was rapidly decreased until about 7% but it had a little change when it is above 7%.

• 열처리공학회지
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• 제34권3호
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• pp.116-121
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• 2021

This study was carried out to investigate the effect of transformation induced martensite on the tensile properties of Fe-20Mn-12Cr-3Ni-3Si alloy. α' and ε-martensite were formed by cold rolling, and these martensite were formed with according to the specific direction, surface relief and partially intersection. With an increasing degree of cold rolling, amount of α'-martensite was slowly increased, whereas amount of ε-martensite was rapidly increased. Volume fraction of ε-martensite formed by cold working was large than α'-martensite. Tensile strength was rapidly increase and elongation was rapidly decreased with an increasing of degree of cold rolling. This means that tensile strengh and elongation was greatly influenced by the volume fraction of ε-martensite formed by cold rolling then α'-martensite.

• 열처리공학회지
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• 제37권3호
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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 (M_s), 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.

• 열처리공학회지
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• 제25권5호
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• pp.233-238
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• 2012

The effect of subzero treatment on the mechanical properties of cold rolled high manganese austenitic stainless steel was investagated. ${\alpha}$'-martensite was formed by cold rolling, and it was formed with surface relief and specific direction or crossing each other. The volume fraction of martensite increased by subzero treatment, and it was increased with longer time of subzero treatment and higher temperature of subzero treatment. The hardness and strength increased by subzero treatment, while the elongation decreased. With the increase of volume fraction of martensite, the hardness and strength was increased steeply with proportional relationship, elongation was decreased slowly. The results show that the hardness and strength was strongly controlled by the volume fraction of martensite, and the elongation was affected by transformation behavior of deformation induced martensite in the initial stage of deformation.

• 열처리공학회지
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• 제32권2호
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• pp.61-67
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• 2019

This study was carried out to investigate the effect of thermo-mechanical treatment on the tensile properties of Fe-20Mn-12Cr-3Ni-3Si alloy with deformation induced martensite transformation. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite, dislocation, stacking fault were formed, and grain size was refined by thermo-mechanical treatment. With the increasing cycle number of thermo-mechanical treatment, volume fraction of ${\varepsilon}$ and ${\alpha}^{\prime}$-martensite, dislocation, stacking fault were increased, and grain size decreased. In 5-cycle number thermo-mechanical treated specimens, more than 10% of the volume fraction of ${\varepsilon}$-martensite and less than 3% of the volume fraction of ${\alpha}^{\prime}$-martensite were attained. Tensile strength was increased and elongation was decreased with the increasing cycle number of thermo-mechanical treatment. Tensile properties of thermo-mechanical treated alloy with deformation induced martensite transformation was affected to formation of martensite by thermo-mechanical treatment, but was large affected to increasing of dislocation and grain refining.