• 한국해양공학회지
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• 제17권2호
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• pp.40-46
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• 2003

The corrosion resistance of super duplex stainless steel on both its fibrous and dispersed phase was investigated. These structures consist of various volume fraction and distribution of austenite structure, which were obtained by changing the heat treatment temperature and cycle. The fibrous phase had higher austenite volume fraction than that of the dispersed phase at the same temperature. Corrosion resistance of super duplex stainless steel was evaluated through an immersion test and an impingement test, using 35% HCI and sea water, respectively. Super duplex stainless steel was compared with STS316L and STS304. The corrosion resistance of super duplex stainless steel was superior to ST316L and STS304. The dispersed phase of super duplex stainless steel was more stabilized than the fibrous phase in corrosion. The magnitude of corrosion rate was in order STS304, STS316L, fibrous phase of super duplex stainless steel and dispersed phase of super duplex stainless steel.

• 동력기계공학회지
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• 제20권1호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.712-716
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• 2003

In the present study, the gas injection system based on air-water model was designed to investigate the behavior characteristics of bubbles injected into a ladle. The parameters such as gas volume fraction and bubble rise velocity were exprementally measured in a gas-liquid flow region. To measure gas volume fraction, an electo-conductivity probe was used and bubble rise velocity was obtained by a high speed CCD camera. Gas volume fraction was symmetric to the axis of nozzle secured on the bottom of a ladle. The bubble rise velocity was calculated for two different experimental conditions. That is, gas flow conditions were following two case: 1) Q = $0.63{\times}10^{-4}$ $m^{3}/s$, 2) $1.26{\times}10^{-4}$ $m^{3}/s$. As a gas injected into the liquid ladle, the liquid-phase region is circulated by bubbles' behavior. The bubble rise velocity was influenced of the circulation flow of liquid phase. As a result, the bubble rise velocity was appeared higher middle region of ladle than near the nozzle.

• 소성∙가공
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• 제8권4호
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• pp.399-406
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• 1999

It is more appropriate to treat that the semi-solid mixture as a single phase material that obeys incompressibility in the global sense and to analyze the liquid flow only locally than the approach based on compressible yield criteria. In the present study, a numerical algorithm of updating the solid volume fraction based on mixture theory has been developed. Finite element analysis of simple upsetting was carried out using the proposed algorithm to investigate the degree of macro-segregation according to friction conditions and compressive strain rates under the isothermal condition. The simulation results were compared to experimental results available in reference to test the validity of the currently proposed algorithm. Since the comparison results show a good agreement it is construed that the proposed algorithm can contribute to the development of numerical analysis of determining the solid volume fraction semi-solid processing.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.146-149
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• 2002

In this study, 2-2 type piezocomposites were made and characteristics as volume fraction of PZT were investigated. The accoustic impedance of 2-2 piezoelectric composites was linearly decreased with decreasing PZT volume fraction. when the volume fraction of PZT was 0.2 the acoustic impedance was 3.2 Mrayl. The electromechanical coupling factor was favourable in comparison with the single phase PZT, and that was about uniformed about 0.68 in the 0.2 to 0.6 of PZT volume fraction.

• 한국표면공학회지
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• 제45권6호
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• pp.284-288
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• 2012

A study on microstructure control of multi-phase steel have been implemented to higher strength with improved formability. However, it is well known that the high strength of steel are susceptible to hydrogen embrittlement. The mechanisms of hydrogen embrittlement is caused by complex interactions. In this paper, the test specimens were fabricated to 5 type of 590DP steels at different levels of volume faction. The hydrogen charging was conducted by electrochemical hydrogen-charge method with varying charging time. The relationship between hydrogen concentration and volume fraction of 590DP steel was established by SP test and SEM-fractography. It was shown that the hydrogen amounts charged in 590DP steels increased with increasing the volume faction of austenite. The maximum loads of the 590DP steels in SP test were sharply decreased with increasing hydrogen charging time. The results of SEM-fractography investigation showed typical brittle-fracture surfaces for hydrogen-charged 590DP steels.

• 한국주조공학회지
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• 제18권3호
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• pp.271-274
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• 1998

Effects of Si and Ni addition on the microstructure and mechanical properties of the Cu-12wt.%Al-5wt.%Fe-1wt.%Mn alloy have been investigated experimentally. Microstructure of the as-cast specimen is found to be refined markedly by additions of Ni and Si. By the addition of Ni, volume fraction of the ${\kappa}$ phase is increased, but volume fraction of the ${\gamma}$ phase is decreased. Hardness is increased with the addition of Ni, due to increasing of ${\kappa}$ phase which is harder than ${\gamma}$ phase. However, Charpy impact value is not significally decreased possibly due to the formation of isolate ${\kappa}$ phase.

• Journal of Welding and Joining
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• 제16권3호
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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 $(Δt_{8/5})$).

• 한국표면공학회지
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• 제26권2호
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• pp.63-70
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• 1993

The mechanical properties of ferrite-martensited dual phases steels are affected by the microstructural factors, such as martensited volume fractions, ferrite grain size, strength ratio, connectivity, etc. Two phase alloys are technologically important. However, there is a lack of understanding as to stress-strain behavior of dual phase alloy in terms of stress-strain behavior of each component phases. The lack of the understanding stems from the complex deformation behavior of two phase alloys. The aim of this study is to rationalize stress-strain behavior of dual phase alloy in terms of the stress-strain behavior of component phase by systematically considering all the factors listed above. It was found that for a given martensite volume fraction, the calculated stress-strain curve was higher for a finer particles size than for a coarse particle sized within the range of the strains considered, and this behavior was seen for all the different volume fraction alloys considered. The calculated stress-strain curves were compared with corresponding experimental curves, and in general, good agreement was found. The maximum difference in flow stress between the calculated and the experimental results occurs at the nearly beginning of the plastic deformation.

• The Korean Journal of Ceramics
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• 제2권1호
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• pp.25-32
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• 1996

Solid electroyte nasion was synthesized by the optimized solid state reaction minimizing the volume fraction of secondary $ZrO_2$ and glassy phases. To compensate for the evaporation of Na and P during heat-treatment, excess Na and P were added to the starting composition $Na_{1+x} Zr_2 Si_x P_{d-x} O_{12}$ (x=2.1). Phases pure nasicon comparable in volume fraction to the one obtaied from sol-gel process were synthesized after the reaction at $1100~1150^{\circ}C$,$ P_{O2}>=0.1-0.15 $$ZrO_2$ increased with the heat-treatment time due to the decomposition of nasicon phase and that of glassy phase increased as partial oxygen pressure decreased. The synthesized nasion showed a good electrical conductivity of $-1{\times}10^{-2}({\omega}{\cdot}cm)^{-1}$ at $350^{\circ}C$.