• Title/Summary/Keyword: High Temperature Deformation Behavior

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Analyses of Densification and Consolidation of Copper Powders during High-Pressure Torsion Process Using Finite Element Method (유한요소해석을 이용한 고압비틀림 공정 중의 구리 분말의 치밀화 및 고형화 거동 분석)

  • Lee, Dong Jun;Yoon, Eun Yoo
    • Journal of Powder Materials
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    • v.22 no.1
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    • pp.6-9
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    • 2015
  • In this study, the behavior of densification of copper powders during high-pressure torsion (HPT) at room temperature is investigated using the finite element method. The simulation results show that the center of the workpiece is the first to reach the true density of copper during the compressive stage because the pressure is higher at the center than the periphery. Subsequently, whole workpiece reaches true density after compression due to the high pressure. In addition, the effective strain is increased along the radius during torsional stage. After one rotation, the periphery shows that the effective strain is increased up to 25, which is extensive deformation. These high pressure and severe strain do not only play a key role in consolidation of copper powders but also make the matrix harder by grain refinement.

Effect of C, Mn and Al Additions on Tensile and Charpy Impact Properties of Austenitic High-manganese Steels for Cryogenic Applications (극저온용 오스테나이트계 고망간강의 인장 및 충격 특성에 미치는 C, Mn, Al 첨가의 영향)

  • Lee, Seung-Wan;Hwang, Byoungchul
    • Korean Journal of Materials Research
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    • v.29 no.3
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    • pp.189-195
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    • 2019
  • The effect of C, Mn, and Al additions on the tensile and Charpy impact properties of austenitic high-manganese steels for cryogenic applications is investigated in terms of the deformation mechanism dependent on stacking fault energy and austenite stability. The addition of the alloying elements usually increases the stacking fault energy, which is calculated using a modified thermodynamic model. Although the yield strength of austenitic high-manganese steels is increased by the addition of the alloying elements, the tensile strength is significantly affected by the deformation mechanism associated with stacking fault energy because of grain size refinement caused by deformation twinning and mobile dislocations generated during deformation-induced martensite transformation. None of the austenitic high-manganese steels exhibit clear ductile-brittle transition behavior, but their absorbed energy gradually decreases with lowering test temperature, regardless of the alloying elements. However, the combined addition of Mn and Al to the austenitic high-manganese steels suppresses the decrease in absorbed energy with a decreasing temperature by enhancing austenite stability.

Load Relaxation and Creep Transition Behavior of a Spray Cast Hypereutectic Al-Si Based Alloy (분무 주조 과공정 Al-Si계 합금의 응력이완 및 Creep 천이 거동)

  • Kim M. S.;Bang W.;Park W. J.;Chang Y. W.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.05a
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    • pp.176-179
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    • 2005
  • Spray casting of hypereutectic Al-Si based alloy has been reported to provide distinct advantages over ingot metallurgy (IM) or rapid solidification/powder metallurgy (RS/PM) process in terms of microstructure refinement. Hypereutectic Al-Si based alloys have been regarded attractive for automotive and aerospace application, due to high specific strength, good wear resistance, low coefficient of thermal expansion, high thermal stability, and good creep resistance. In this study, hypereutectic Al-25Si-2.0Cu-1.0Mg alloy was prepared by OSPREY spray casting process. High temperature deformation behavior of the hypereutectic Al-Si based alloy has been investigated by applying the internal variable theory proposed by Chang et al. The change of strain rate sensitivity and Creep transition were analyzed by using the load relaxation test and constant creep test.

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Deformation Behavior of MEMS Gyroscope Package Subjected to Temperature Change (온도변화에 따른 MEMS 자이로스코프 패키지의 미소변형 측정)

  • Joo Jin-Won;Choi Yong-seo;Choa Sung-Hoon;Kim Jong-Seok;Jeong Byung-Gil
    • Journal of the Microelectronics and Packaging Society
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    • v.11 no.4 s.33
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    • pp.13-22
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    • 2004
  • In MEMS devices, packaging induced stress or stress induced structure deformation become increasing concerns since it directly affects the performance of the device. In this paper, deformation behavior of MEMS gyroscope package subjected to temperature change is investigated using high-sensitivity moire interferometry. Using the real-time moire setup, fringe patterns are recorded and analyzed at several temperatures. Temperature dependent analyses of warpages and extensions/contractions of the package are presented. Linear elastic behavior is documented in the temperature region of room temperature to $125^{\circ}C$. Analysis of the package reveals that global bending occurs due to the mismatch of thermal expansion coefficient between the chip, the molding compound and the PCB. Detailed global and local deformations of the package by temperature change are investigated, concerning the variation of natural frequency of MEMS gyro chip.

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Elevated Temperature Deformation Behavior in an AZ31 Magnesium Alloy

  • Yang Kyoung-Tak;Kim Ho-Kyung
    • Journal of Mechanical Science and Technology
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    • v.20 no.8
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    • pp.1209-1216
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    • 2006
  • An AZ31 magnesium alloy was tested at constant temperatures ranging from 423 to 473 K (0.46 to 0.51 Tm) under constant stresses. All of the creep curves exhibited two types depending on stress levels. At low stress (${\sigma}/ G < 4 {\times}10^{-3}$), the creep curve was typical of class A (Alloy type) behavior. However, at high stresses (${\sigma}/ G > 4 {\times}10^{-3}$), the creep curve was typical of class M (Metal type) behavior. At low stress level, the stress exponent for the steady-state creep rate was of 3.5 and the true activation energy for creep was 101 kJ/mole which is close to that for solute diffusion. It indicates that the dominant deformation mechanism was glide-controlled dislocation creep. At low stress level where n=3.5, the present results are in good agreement with the prediction of Fridel model.

Effect of Strain Rate on Microstructure Formation Behavior of M1 Magnesium Alloy During High-temperature Deformation (변형속도에 따른 M1 마그네슘 합금의 고온변형 중 미세조직 형성 거동)

  • Lee, Kyujung;Kim, Kwonhoo
    • Journal of the Korean Society for Heat Treatment
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    • v.32 no.1
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    • pp.1-11
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    • 2019
  • In this study, microstructure evolution and crystallographic orientation are investigated under various deformation conditions in M1 magnesium alloy. M1 magnesium ingot was rolled at 673 K with the rolling reduction of 30%. The compression test specimens were machined out from rolled plate, and then the specimens were annealed at 823 K for 1h. Uniaxial compression tests were conducted at 723 K and under the strain rate ranging from $5.0{\times}10^{-4}s^{-1}$ to $5.0{\times}10^{-2}s^{-1}$ up to a true strain of -1.0. For observation of crystal orientation distribution, EBSD measurement was performed. Occurrence of the dynamic recrystallization and grain boundary migration were confirmed in all case of the specimens. The distribution of the grains is not uniformed in the experimental conditions.

High Temperature Deformation Behavior of Ti-Al Intermetallic Compound and Orientation Distribution of Lamellae Structure (Ti-Al금속간화합물의고온변형거동및라멜라조직의결정방위분포)

  • Park Kyu-Seop;Kang Chang-Yong;Lee Keun-Jin;Chung Han-Shik;Jung Young-Guan;Fukutomi Hiroshi
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.10
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    • pp.162-169
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    • 2004
  • High temperature uniaxial compression tests in the alpha single phase region were carried out on the Ti -43mo1%Al intermetallic compound, in order to obtain oriented lamellar microstructure. The compression deformation temperatures and strain rates are from 1573k to 1623k and 1.0x10$^{-4}$ s to 5.0x10$^{-3}$ s, respectively. Fully lamellar microstructure was observed after the uniaxial compression deformation in a single phase region followed by cooling to room temperature. Lamellar colony diameter depended on strain rates and test temperatures. The diameter varied between 8601m and 300fm. Stress-strain curve showed a work softening and the size of lamellar colony diameter varied depending on peak stresses. This shows the occurrence of dynamic recrystallization. Texture measurements after the uniaxial compression deformation, showed the development of fiber during dynamic recrystallization. It is seen that the area for the maximum pole density existed in 35 degrees away from the compression plane. The texture sharpens with a decrease in strain rate