• Korean Journal of Materials Research
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• v.25 no.1
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• pp.9-15
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• 2015

The effect of retained and reversed austenite on the damping capacity in high manganese stainless steel with two phases of martensite and austenite was studied. The two phase structure of martensite and retained austenite was obtained by deformation for various degrees of deformation, and a two phase structure of martensite and reverse austenite was obtained by reverse annealing treatment for various temperatures after 70 % cold rolling. With the increase in the degree of deformation, the retained austenite and damping capacity rapidly decreased, with an increase in the reverse annealing temperature, the reversed austenite and damping capacity rapidly increased. With the volume fraction of the retained and reverse austenite, the damping capacity increased rapidly. At same volume of retained and reversed austenite, the damping capacity of the reversed austenite was higher than the retained austenite. Thus, the damping capacity was affected greatly by the reversed austenite.

• Journal of Ocean Engineering and Technology
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• v.23 no.3
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• pp.40-45
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• 2009

With the increase in the annealing temperature, the volume fraction of austenite phase increased and the volume fraction of ferrite phase decreased. In compliance with the addition of N, not only the volume fraction of austenite phase was increased but also the austenite structure was made larger. Volume fraction of ${\sigma}$ phase was increased by decreasing of the volume fraction of ferrite phase, with the increase in the aging time and in compliance with the addition of N. As increasing in volume fraction of ${\sigma}$ phase, tensile strength and hardness increased, while elongation and impact value decreased. Elongation slowly decreased and impact value rapidly decreased at the early stage of aging. By the added N, tensile strength, elongation, hardness and impact value was increased.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.36-41
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• 2016

Effects of austenite on the pitting corrosion in 202 stainless steel with two phase of austenite and martensite were investigated through the electrochemical polarization test. Two phases structures of martensite and austenite were obtained by reversed annealing treatment at the range of $500^{\circ}C-700^{\circ}C$ for 10min. in 70% cold-rolled 202 stainless steel. Volume fraction of reversed austenite has increased rapidly with an increase of annealing temperature. Pitting corrosion has arisen mainly on martensite phase in 202 stainless steel with two phases of austenite and martensite. Pitting current density has decreased with an increase of volume fraction of austenite. Consequently, pitting corrosion at martensite has occurred largely with an increase of volume fraction of austenite. Pitting corrosion was affected by volume fraction of austenite.

• Journal of Power System Engineering
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• v.19 no.1
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• pp.70-75
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• 2015

The influence of reversed austenite on the damping capacity in austenitic stainless steel with two phase of martensite and reversed austenite was investigated. The two phases of deformation induced martensite and reversed austenite was obtained by an reverse annealing treatment at $500^{\circ}C{\sim}700^{\circ}C$ for various time after 70% cold rolling. With an increase of the reverse annealing treatment temperature and time, volume fraction of reversed austenite was rapidly increased. With an increase of volume fraction of reveresd austenite, damping capacity was rapidly increased. At same volume of reveresd austenite, damping capacity of reversed austenite obtained by reverse annealing treatment at $700^{\circ}C$ for various time was higher then reveresd austenite obtained by reverse annealing treatment at $500^{\circ}C{\sim}700^{\circ}C$ for 10min. Thus, the damping capacity was affected greatly by reversed austenite obtained by annealing treatment at $700^{\circ}C$ for various time.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.114-120
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• 2013

This study was carried out to investigate the relationship between mechanical properties and damping capacity in high manganese austenitic stainless steel with two phase mixed structure of reversed austenite and deformation induced martensite. Reversed austenite of ultra-fine grain size less than $0.3{\mu}m$ was obtained by reversion treatment. Two phase structure of deformation induced martensite and reversed austenite was obtained by annealing treatment at range of $500^{\circ}C{\sim}700^{\circ}C$ for various time in cold rolled high manganese austenite stainless steel. In stainless steel with two phase mixed structure of martensite and austenite, damping capacity decreased rapidly with the increasing hardness and strength. With the increasing elongation, damping capacity was increased rapidly and then, slowly increased.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.4
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• pp.200-205
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• 2015

Effects of austenite on the uniform corrosion in the solution of $1\;N\;H_2SO_4$ were investigated through the electrochemical polarization test. Two phases structures of martensite and austenite were obtained by annealing treatment at the range of $500^{\circ}C{\sim}700^{\circ}C$ for 10min. in 70% cold-rolled 202 stainless steel. Volume fraction of reversed austenite increased rapidly with an increase of annealing temperature. Uniform Corrosion was occur mainly on martensite phase in 202 austenitic stainless steel with two phase of austenite and martensite. Corrosion current density increased with an increase of volume fraction of austenite, therefore uniform corrosion was affected by volume fraction of austenite

• Journal of Powder Materials
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• v.26 no.5
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• pp.389-394
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• 2019

In the present study, we have investigated the effect of sintering process conditions on the stability of the austenite phase in the nanocrystalline Fe-5wt.%Mn-0.2wt.%C alloy. The stability and volume fraction of the austenite phase are the key factors that determine the mechanical properties of FeMnC alloys, because strain-induced austenite-martensite transformation occurs under the application of an external stress at room temperature. Nanocrystalline Fe-5wt.%Mn-0.2wt.%C samples are fabricated using the spark plasma sintering method. The stability of the austenite phase in the sintered samples is evaluated by X-ray diffraction analysis and hardness test. The volume fraction of austenite at room temperature increases as the sample is held for 10 min at the sintering temperature, because of carbon diffusion in austenite. Moreover, water quenching effectively prevents the formation of cementite during cooling, resulting in a higher volume fraction of austenite. Furthermore, it is found that the hardness is influenced by both the austenite carbon content and volume fraction.

• Korean Journal of Materials Research
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• v.17 no.1
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• pp.37-42
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• 2007

The effects of immersion time in the liquid nitrogen and deformation-induced martensitic transformation on the behavior of austenite stainless steels used for the hydrogen storage tank of auto-mobile at cryogenic temperature were investigated. With increasing of immersion time in the liquid nitrogen, the tensile strength of all austenite stainless steels at cryogenic temperature was increased because the martensite transformation of unstable austenite. The restraint of crack generation ana transmission also increased the tensile strength by the active ${\alpha}'$ transformation. The elongation decreasing of 321 steel is not the mechanical deformation of austenite phase but the stress induced martensite phase during the tensile test.

• Transactions of Materials Processing
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• v.26 no.1
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• pp.48-54
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• 2017

The dissolution and precipitation of Nb, which has been known as strong carbide-forming element, play a key role in controlling phase transformation kinetics of microalloyed steels. In this study, we analyzed both numerically and experimentally the precipitation behavior of Nb-microalloyed steel and its effect on the austenite decomposition during cooling. Nb precipitation in austenite matrix could be predicted by the thermo-kinetic software MatCalc, in which interfacial energy between precipitate and matrix is calculated. The simulated precipitation kinetics fairly well agrees with the experimental observations by TEM. Austenite decomposition, which is strongly affected by Nb precipitation during cooling, was measured by dilatometry and was modeled on the basis of a Johnson-Mehl-Avrami-Kolmorgorov(JMAK) equation. It was confirmed that the dissolved Nb delays the austenite decomposition, whereas, the precipitated Nb accelerates phase transformation during the austenite decomposition.

• Korean Journal of Materials Research
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• v.17 no.12
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• pp.654-659
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• 2007

Austenite precipitation behavior was studied with solidification rates and alloying contents, N and Cr, in duplex stainless steels by directional solidification. Directional solidification experiments were carried out with solidification rates, $1{\sim}100mm/s$, and N and Cr contents, $0{\sim}0.27wt.%,\;25{\sim}28wt.%$ respectively, in a duplex stainless steel, CD4MCU. As the solidification rate increases, the dendrite spacing reduced and the austenite phase in the ferrite matrix became finer. The volume fraction of austenite phase increased and its shape went to be round with increasing nitrogen contents in duplex stainless alloys. The Cr alloying element, even though it is a ferrite former, showed to enhance the nitrogen solubility in the alloy and caused the austenite round and finer. Also, Cr was supposed to decrease the austenite volume fraction, but it increased the austenite slightly due to increasing nitrogen solubility during solidification.