• Title/Summary/Keyword: High temperature phase

Search Result 2,686, Processing Time 0.029 seconds

Fabrication of Bi-based High-Tc superconducting thin films by 4-target RF magnetron sputtering methods (4원타깃 RF마그네트론 스퍼터링법을 이용한 Bi계 고온 초전도체 박막의 제작)

  • 이현수;강형곤;임성훈;한병성
    • Electrical & Electronic Materials
    • /
    • v.10 no.9
    • /
    • pp.869-875
    • /
    • 1997
  • Bi based superconducting thin films were fabricated by 4-target RF magnetron sputtering using the method of controlling the on-off time. These thin films showed better crystal structures. The ratio of Cu/Bi decreased but the critical temperature increased with increasing the temperature of the substrate. High temperature phase low temperature of the substrate. High temperature phase low temperature phase and semiconducting phase can be formed by controlling the on-off time of the shutter respectively.

  • PDF

Application of the Through-Transmitted Ultrasonic Signal for the Identification of Two-Phase Flow Patterns in a Simulated High Temperature Vertical Channel

  • Chu In-Cheol;Song Chul-Hwa;Baek Won-Pil
    • Nuclear Engineering and Technology
    • /
    • v.36 no.1
    • /
    • pp.12-23
    • /
    • 2004
  • In the present study a new measurement technique has been developed, which uses an ultrasonic transmission signal in order to identify the vertical two phase flow pattern. The ultrasonic measurement system developed in the present study not only provides the information required for the identification of vertical two phase flow patterns but also makes real time identification possible. Various vertical two phase flow patterns such as bubbly, slug, churn, annular flow etc. have been accurately identified with the present ultrasonic measurement system under atmospheric condition. In addition, the present test apparatus can practically simulate the ultrasonic propagation characteristics under high temperature and high pressure systems. Therefore, it is expected that the present ultrasonic flow pattern identification technique could be applicable to the vertical two phase flow systems under high temperature and high pressure conditions.

Temperature and Property Control of High Strength Steel in Hot Strip Mills (열간압연 고강도강의 온도 및 재질제어)

  • Park, Cheol-Jae
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.20 no.6
    • /
    • pp.817-823
    • /
    • 2011
  • This paper proposes a cooling stop temperature control(CST) and a phase transformation control(PTR) which aim at obtaining the uniform temperature and quality along the longitudinal direction of the high strength steel on the run-out table(ROT) process. The problems of the temperature control are analyzed for the conventional steel and the new control concepts are derived from a time-temperature transformation(TTT) diagram. The proposed control technologies are verified from the simulation results under the temperature prediction model by the heat transfer governing equation, and the temperature estimation simulator. It is shown through the field test of the hot strip mills that the phase transformation ratio of the high strength steel is considerably improved by the proposed temperature controls.

A study on the Microstructure and Mechanical Properties of Two-Phase (($NiAl+Ni_3Al$) 2상 합금의 미세 조직과 기계적 특성에 관한 연구)

  • Lee, Jong-Hun;Choe, Byeong-Hak;Lee, Nam-Jin;Kim, Hak-Min;Lee, Jin-Hyeong
    • 연구논문집
    • /
    • s.24
    • /
    • pp.161-174
    • /
    • 1994
  • The Ni-Al intermetallic compound that has the greatest potential to be commercialized shows the high ductility at room temperature with the addition of boron, but has extremely low ductility at high temperature and oxidation environment. On this research work, the changes of microstructure and compressive fracture properties were studied in ($NiAl+Ni_3Al$) two-phase alloys. The precipitation behavior of $Ni_3Al$ after solution treatment at $1300^\circC$ for 14hrs and aging treatment at $800^{\circ}C$ for 14hrs was varied with Al content in ($NiAl+Ni_3Al$) two-phase alloys. These microstructure could be modified dramatically by suitable heat treatments. Martensite or martensite plus $Ni_3Al$ microstructure was obtained upon oil quenching from $1300^\circC$. Aging of Martensite at $800^\circC$ resulted in the $Ni_3Al$ plus NiAl phase. The compressive fracture strength and compressive fracture strain were improved by the $Ni_3Al$ plus NiAl phase mixtures at room temperature and $1100^\circC$. Microcracks are observed mostly in the region of NiAl and the interface of $NiAl-Ni_3Al$ phase after compressive test at room temperature. In the case of high temperature compressive test, microcracks are formed in the region of $Ni_3Al$ phase.

  • PDF

Analysis of the Strength Property for TiC-Mo Composites at High Temperature

  • Shin, Soon-Gi
    • Korean Journal of Materials Research
    • /
    • v.24 no.4
    • /
    • pp.201-206
    • /
    • 2014
  • TiC-21 mol% Mo solid solution (${\delta}$-phase) and TiC-99 mol% Mo solid solution (${\beta}$-phase), and TiC-(80~90) mol% Mo hypo-eutectic composite were deformed by compression in a temperature range from room to 2300 K and in a strain rate range from $4.9{\times}10^{-5}$ to $6.9{\times}10^{-3}/s$. The deformation behaviors of the composites were analyzed from the strengths of the ${\delta}$- and ${\beta}$-phases. It was found that the high strength of the eutectic composite is due primarily to solution hardening of TiC by Mo, and that the ${\delta}$-phase undergoes an appreciable plastic deformation at and above 1420 K even at 0.2% plastic strain of the composite. The yield strength of the three kinds of phase up to 1420 K is quantitatively explained by the rule of mixture, where internal stresses introduced by plastic deformation are taken into account. Above 1420 K, however, the calculated yield strength was considerably larger than the measured strength. The yield stress of ${\beta}$-phase was much larger than that of pure TiC. A good linear relationship was held between the yield stress and the plastic strain rate in a double-logarithmic plot. The deformation behavior in ${\delta}$-phase was different among the three temperature ranges tested, i.e., low, intermediate and high. At an intermediate temperature, no yield drop occurred, and from the beginning the work hardening level was high. At the tested temperature, a good linear relationship was held in the double logarithmic plot of the yield stress against the plastic strain rate. The strain rate dependence of the yield stress was very weak up to 1273 K in the hypo-eutectic composite, but it became stronger as the temperature rose.

In Situ Observation of Domain Structure of $NaNbO_3$ Using Polarizing Microscope (편광 현미경을 이용한 Sodium Niobate 단결정의 분역 구조 관찰)

  • 정선태
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.12
    • /
    • pp.1235-1239
    • /
    • 1997
  • Sodium niobate single crystals were grown by high temperature solution growth with Na2O/B2O3 flux. The phase transitions and domain structures of sodium niobate were observed using transmission polarizing microscope from room temperature to $650^{\circ}C$. There was imperfect extinction region within as-grown crystals and this area could be removed by heat treatment. The area existed within crystal till 3$65^{\circ}C$, in which temperature the space group of sodium niobate is changed from Pbma to Pmnm. The phase transition from Pbma to Pmnm happened abruptly with changing domain structure. At 48$0^{\circ}C$, 52$0^{\circ}C$ and 572$^{\circ}C$, the colors and walls of domains were changed. All domains disappeared and the space group of sodium niobate was changed from P4/mbm to Pm3m at 64$0^{\circ}C$. When sodium niobate changed from high temperature phase to low temperature phase, the memory effect of domain structure was not observed.

  • PDF

Effect of Double Aging on Microstructure and Mechanical Properties of Ag Added magnesium Alloys (Ag첨가 마그네슘 합금의 이중열처리에 따른 미세조직 및 기계적 특성변화)

  • Lee, Byeong-Deok;Baek, Ui-Hyun;Jang, Kyoung-soo;Han, Jeong-Whan;Son, Hyeon-taek
    • Korean Journal of Metals and Materials
    • /
    • v.49 no.6
    • /
    • pp.440-447
    • /
    • 2011
  • To improving the mechanical properties of Mg alloys at high temperature, we investigated the mechanical properties at high temperature and the change of microstructure of Mg-6 wt%Zn-0.4 wt%Mn and Mg-6 wt%Zn-0.4 wt%Mn-1 wt%Ag alloys on age treatment that have a stable MgZn phase at high temperature and $AgMg_4$ improving yield stress. In order to predict thermodynamic data of Mg alloys, a phase diagram and precipitation phase were calculated using a thermodynamic program, and it was confirmed that the MgZn and $AgMg_4$ phase existed as main precipitation in this alloys. The experimental data examined using DSC and XRD were comparable with the calculated data for reliability. In order to analysis the microstructure and precipitate phase during aging treatment, it was measured by SEM/EDS and TEM. Lastly, mechanical properties of the MgZn and $AgMg_4$ phase were measured by a tensile test at high temperature.

Aging Behavior and Effect of Heat Treatment on High Temperature Mechanical Properties in Ti-15V-3AI-3Cr-3Sn (Ti-15V-3Al합금의 시효거동과 열처리에 따른 고온 기계적 특성)

  • Lee Jae Won;Lee Back-Hee;Lee Kyu Hwan;Kim Young Do
    • Korean Journal of Materials Research
    • /
    • v.14 no.1
    • /
    • pp.13-18
    • /
    • 2004
  • Titanium alloys are the one of promising candidate materials for medium high temperature parts in the aircraft, automobile, petrochemistry and electrochemistry because of their high strength with low density in medium high temperature. In this study, the effects of aging and heat treatments on the mechanical properties of Ti-15-3 alloy in medium high temperature, which was $400^{\circ}C$, were studied. Solid solution treatment was performed at $8000^{\circ}C$ of $\beta$ phase region for 1 h and the alloy was quenched in water. The alloy was aged at $5000^{\circ}C$ of $\alpha$ and $\beta$ two-phase region for 1, 2, 4, 8, ... and 100 h to increase the mechanical property. The $\beta$ single phase was observed at all parts of specimens in Ti-15-3 alloy after ST. As the aging at $500^{\circ}C$, fine precipitates of a phase was generated from matrix of $\beta$ phase and the microstructure was consisted of weaving structure such as Widmanstiitten a phase. The most suitable aging time is 24h in$ 400^{\circ}C$. At this time, strength is 1164 MPa and elongation is about 12%. In room temperature, elongation of Ti-15-3 alloy aged at $500^{\circ}C$ for 16 h is poor (=3%) in spite of high tensile strength (1458 MPa).

Deformation Properties of TiC-Mo Eutectic Composite at High Temperature (TiC-Mo 공정복합재료의 고온 변형특성)

  • Shin, Soon-Gi
    • Korean Journal of Materials Research
    • /
    • v.23 no.10
    • /
    • pp.568-573
    • /
    • 2013
  • The deformation properties of a TiC-Mo eutectic composite were investigated in a compression test at temperatures ranging from room temperature to 2053 K and at strain rates ranging from $3.9{\times}10^{-5}s^{-1}$ to $4.9{\times}10^{-3}s^{-1}$. It was found that this material shows excellent high-temperature strength as well as appreciable room-temperature toughness, suggesting that the material is a good candidate for high-temperature application as a structure material. At a low-temperature, high strength is observed. The deformation behavior is different among the three temperature ranges tested here, i.e., low, intermediate and high. At an intermediate temperature, no yield drop occurs, and from the beginning the work hardening level is high. At a high temperature, a yield drop occurs again, after which deformation proceeds with nearly constant stress. The temperature- and yield-stress-dependence of the strain is the strongest in this case among the three temperature ranges. The observed high-temperature deformation behavior suggests that the excellent high-temperature strength is due to the constraining of the deformation in the Mo phase by the thin TiC components, which is considerably stronger than bulk TiC. It is also concluded that the appreciable room-temperature toughness is ascribed to the frequent branching of crack paths as well as to the plastic deformation of the Mo phase.

High temperature deformation behavior of $\alpha\;and\;\beta$ phase of Ti-6Al-4V alloy with an equiaxed microstructure (등축정 Ti-6Al-4V 합금의 $\alpha,\;\beta$ 구성상의 고온변형거동 규명)

  • Lee, You-Hwan;Yeom, Jong-Taek;Park, Nho-Kwang;Lee, Chong-Soo;Kim, Jeoung-Han
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2005.05a
    • /
    • pp.295-298
    • /
    • 2005
  • High temperature deformation behavior of $\alpha\;and\;\beta$ phase of Ti-6Al-4V was investigated within the framework of a self-consistent approach at various temperature ranges. To examine the flow behavior of u-phase, Ti-7.0Al-1.5V alloy was used, whose chemical composition is close to that of the $\alpha$ phase in Ti-6Al-4V at hot working temperatures. The flow stress of $\beta$ phase was predicted by using self-consistent approach. The flow stress of $\alpha$ phase was higher than that of $\beta$ phase above $750^{\circ}C$, while the $\beta$ phase revealed higher flow stress than a phase at $650^{\circ}C$. It was found that the relative strength and strain rate ratio between $\alpha\;and\;\beta$ phase significantly varied with temperature. From this approach, the mode for grain matrix deformation was proposed as a mixed type of both iso-stress and iso-strain rate modes.

  • PDF