• 한국자동차공학회논문집
• /
• 제8권4호
• /
• pp.141-148
• /
• 2000

As the steel plates used for automobile safety the TRIP-assisted multiphase steels are being introduced to automobile industry with respect to their remarkable mechanical properties for the combination of high strength and large elongation. This multiphase structure is generated by two stage heat treatment (intercritical annealing & isothermal treatment) The metastable retained austenite can be transformed to martensite when plastically deformed which results in TRIP effect. Actually the microstructure of TRIP-assisted steels consist of a fine dispersite. There present discussion deals with bainite reaction kinetics of austenite in the process o f two stage heat treatment. In relation to bainite transformation the characteristics of bainite reaction is found to be influenced by the bainite tempering temperature and also by the relative rate in which carbides precipitate within residual austenite.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제15권2호
• /
• pp.243-248
• /
• 2015

We prepared semi-insulating CdTe for radiation detectors by isothermal annealing of single crystals grown by Bridgeman technique in a sealed quartz container filled with Sn vapor. The resistivity of CdTe:Sn samples thus obtained was of order of $10^{10}Ohm{\cdot}cm$ at room temperature with electrons lifetime of $2{\times}10^{-8}$ s, which is appropriate for the applications desired. Analysis of electric transport characteristics depending on temperature, sample thickness and voltage applied revealed the presence of traps with concentration of about $(4-5){\times}10^{12}cm^{-3}$ with the corresponding energy level at 0.8 - 0.9 eV counted from the bottom of conduction band. The conductivity was determined by electron injection from electrodes in space charge limited current mode.

• 대한금속재료학회지
• /
• 제46권2호
• /
• pp.53-57
• /
• 2008

This study examined the role of excess free volume on the corrosion resistance of an amorphous alloy. Corrosion behaviors were monitored on the amorphous alloys, of which amount of free volume was controlled via the isothermal annealing below the glass transition temperature, using immersion tests and potentiodynamic polarization tests in HCl aqueous solutions. It was found that the corrosion resistance of the amorphous alloy is improved by reducing the amount of excess free volume. The possible reason explaining the experimental result was discussed from the viewpoint of the internal energy associated with the annihilation of excess free volume.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 1998년도 추계학술발표회 초록집
• /
• pp.32-32
• /
• 1998

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 1999년도 추계연구발표회 논문개요집
• /
• pp.132-133
• /
• 1999

• Applied Microscopy
• /
• 제45권1호
• /
• pp.16-22
• /
• 2015

The reaction kinetics of the growth of Ni germanide in the Ni/Zr-interlayer/Ge system was investigated using isothermal in situ annealing at three different temperatures in a transmission electron microscope. The growth rate of Ni germanide in the Ni/Zr-interlayer/Ge system was determined to be diffusion controlled and depended on the square root of the time, with the activation energy of $1.04P{\pm}0.04eV$. For the Ni/Zr-interlayer/Ge system, no intermediate or intermixing layer between the Zr-interlayer and Ge substrate was formed, and thus the Ni germanide was formed and grew uniformly due to Ni diffusion through the diffusion path created in the amorphous Zr-interlayer during the annealing process in the absence of any intermetallic compounds. The reaction kinetics in the Ni/Zr-interlayer/Ge system was affected only by the Zr-interlayer.

• 한국재료학회지
• /
• 제11권6호
• /
• pp.483-491
• /
• 2001

냉간가공된 Zr 합금을 $575^{\circ}C$에서 $650^{\circ}C$의 온도범위에서 유지시간을 달리하여 열처리하는 동안에 발생하는 회복 및 재결정 거동을 TEP(ThermoElectric Power)와 미소경도 분석을 통하여 연구하였다. 냉간가공과 열처리에 따른 합금의 회복 및 재결정온 격자결함, 공공, 전위, 적층결함 등이 소멸함에 따라 TEP가 증가하는 거동을 보였다. 이러한 TEP 분석은 미소경도 분석에 비해 재결정의 완료를 정확하게 예측할 수 있었으며, 특히, Zr-0.4Nb-xSn합금에서는 미소경도 분석으로 쉽게 구분하기 어려운 회복 및 재결정 단계를 명확하게 나타내었다. TBP와 미소경도 분석을 이용한 Zr-base합금의 재결정 거동에 따르면, Sn을 첨가하는 경우에 Sn이 치환형 고용체로 존재하기 때문에 이로 인한 응력장과 전위와의 상호작용에 기인하여 회복이 지연되는 현상을 가져왔으며, Nb함량을 증가시키는 경우에는 재결정 지연 효과가 미미하였으나, 석출물 형성에 의한 결정립 성장의 지연효과가 크게 나타났다.

• 한국재료학회지
• /
• 제11권2호
• /
• pp.132-136
• /
• 2001

기계적 합금화 공정을 이용하여 열전재료$FeSi_2$분말을 제조하여 열간압축법을 사용하여 성형하였다. 열간압축 성형된 $FeSi_2$는 열전특성을 나타내는 $\beta$-$FeSi_2$ 상 및 상변태가 완료되지 않은 $\alpha$-$Fe_2$$Si_{5}$와 $\varepsilon$-FeSi의 혼합상으로 이루어져 있음이 확인되었다. 열전재료로의 $\beta$-$FeSi_2$ 상변태 유도를 위해 항온열처리를 행하여 상변태 조건을 조사하였다. SEM, TEM, XRD, DTA 등을 이용하여 상변태 거동을 분석한 결과, $830^{\circ}C$에서 24시간 진공 항온열처리 후 단상의 $\beta$-FeSi$_2$ 상을 얻을 수 있었다. 항온열처리 전의 열간압축 성형체와 상변태가 완료된 $\beta$-FeSi$_2$의 기계적 성질과 열전 특성을 측정하여 비교 분석하였다.

• 열처리공학회지
• /
• 제10권1호
• /
• pp.1-9
• /
• 1997

The variation of the mechanical properties and the formation of retained austenite with heat treatment conditions in austempered Si bearing carbon steels has been investigated. In the case of a steel containing 0.35C-1.48Si-0.95Mn, it has been found that a feather shape bainite structure of lath are obtained under a isothermal treated condition at just below the Ms temperature, and the martensite, bainitic ferrite and retained austenite of second phase particles on the ferrite matrix for a isothermal treated steels after intercritical annealing are precipitated in a linked shape. The retained austenite with $2{\mu}m$ size induced as TRIP is found to increase with increasing the formation rate of retained austenite for the intercritical annealing and high Si containing steels. The tensile strength is increased as austempering temperature increases in all isothermal treatment temperature, whereas the elongation is shown to roughly decrease as the tensile strength increases. The values of tensile strength-elongation balance have showed a marked dependence upon the elongation rather than the tensile stregth, and their values are increased for high Si containing steels and intercritical annealing condition. The most optimum result has been shown to be the tensile stregth-elongation balance of $2882.4kgf/mm^2.%$ and the elongation of 33.3% for a "B" steel in the heat treating temperature range of $780{\sim}370^{\circ}C$.

• 한국분말재료학회지
• /
• 제4권1호
• /
• pp.48-54
• /
• 1997

NiAl powders containing oxide dispersoids have been produced by mechanical alloying process in a controlled atmosphere using high energy attrition mill. The powders have been consolidated by hot extrusion and hot pressing followed by isothermal annealing to induce microstructure coarsening to improve high temperature properties. Grain growth and dispersoid coarsening kinetics have been investigated as functions of annealing time and temperature. Coarsening of dispersion strengthen NiAl and dispersoid has been discussed. Some clues of secondary recrystallization have been investigated. Mechanical property measurements have been also made and correlated with the microstructures.