• Title, Summary, Keyword: Superplastic formability

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Characterization of Superplasticity Using Cone-Type Bulge Test (원뿔형 금형을 이용한 초소성 변형 특성 평가)

  • Kwon Y.-N.;Lee S. J.;Lee Y. S.;Lee H. S.;Lee J. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.180-183
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    • 2004
  • Superplastic formability depends on flow parameters such as temperature, strain rate, strain and stress, microstructures. Usually, superplastic properties of materials are characterized with using a uni-axial tension testing. However, superplastic sheet is formed under mutiaxial loading condition in most forming practices. In the present study, superplastic characteristics of A15083 alloys were determined with using both a uni-axial and biaxial bulging tests. Specially, cone-type die was used to achieve constant strain rate under constant pressure condition. Even though constant strain rate under a certain pressure was achieved only approximately, a cone-type bulging test was found to be quite beneficial to get a multiaxial formability of superplastic materials.

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A Study on the Micro-Formability of Al 5083 Superplastic Alloy Using Micro-Forging System (마이크로 단조 시스템을 이용한 Al 5083 초소성 합금의 마이크로 성형성에 관한 연구)

  • Son S. C.;Kang S. G.;Park K. Y.;Na Y. S.;Lee J. H.
    • Transactions of Materials Processing
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    • v.14 no.5
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    • pp.432-438
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    • 2005
  • Among the most of manufacturing process, plastic deformation method offers a significant advantage in productivity and enable mass production with controlled quality and low cost. From the point of view, micro forming is a well suited technology in manufacturing very small metallic parts, in particular for mass production, as they are required in many industrial products. Meanwhile, Al 5083 superplastic alloy with very small grains has a great advantage in achieving micro deformation under low stress due to its relatively low strength at a specific high temperature range. This paper describes the micro formability of Al 5083 superplastic alloy and its application to die forging of micro patterns. Micro formability tests of Al 5083 superplastic alloy were carried out with the specially designed micro forging system by using V-grooved micro dies and pyramidal dies made of (100) silicon. With these dies, micro forging was conducted by varying the applied load, material temperature and forging time The micro formability of Al 5083 superplastic alloy was evaluated by comparing $R_f$ value, where $R_f\;=\;A_f/A_v$ ($A_v$ : cross-sectional area of the flowed metal, $A_v$ : cross sectional area of V-groove). The micro formability of 3 dimensional Patterns was also evaluated using Pyramidal type micro dies.

A Study on the Micro Vibration Forming of Al-based Superplastic Alloy and Zr-based Bulk Metallic Glass (Al계 초소성합금과 Zr계 비정질합금의 마이크로 진동성형에 관한 연구)

  • Son, Seon-Cheon;Park, Kyu-Yeol;Na, Young-Sang
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.6
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    • pp.193-200
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    • 2007
  • Micro forming is a suited technology to manufacture very small metallic parts(several $mm{\sim}{\mu}m$). Al5083 superplastic alloy with very small grains has a great advantage in achieving micro deformation under low stress due to its relatively low strength at a specific high temperature range. Micro forming of $Zr_{62}Cu_{17}Ni_{13}Al_8$ bulk Metallic glass(BMG) as a candidate material for this developing process are feasible at a relatively low stress in the supercooled liquid state without any crystallization during hot deformation. In this study, the micro formability of Al5083 superplastic alloy and bulk metallic glass, $Zr_{62}Cu_{17}Ni_{13}Al_8$, was investigated with the specially designed micro vibration forming system using pyramid-shape, V-shape and U-shape micro die pattern. With these dies, micro vibration forming was conducted by varying the applied load, time. Micro formability was estimated by comparing the hight of formed shape using non-contact surface profiler system. The vibration load effect to metal flow in the micro die and improve the micro formability of Al5083 superplastic alloy and $Zr_{62}Cu_{17}Ni_{13}Al_8$ bulk Metallic glass(BMG).

Cavitation Behavior of AZ31 Sheet during Gas Blow Forming (AZ31 합금의 부풀림 성형시 공공의 거동)

  • Kim, S.H.;Kang, N.H.;Kwon, Y.N.
    • Transactions of Materials Processing
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    • v.20 no.8
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    • pp.601-610
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    • 2011
  • Based on the facts that AZ31 magnesium alloy can be blow formed just like superplastic aluminum alloys and that most superplastic alloys fail by cavitation, the present study was undertaken to investigate the cavitation behavior of a fine-grained AZ31 sheet during blow forming at the elevated temperature. Other points of interest included the much lower strain rate and temperature dependencies of the magnesium alloy compared with conventional superplastic alloys. It was also aimed to find if cavitation in the AZ31 alloy can be suppressed by hydrostatic pressure, as is the case in most superplastic alloys. Interestingly, the application of hydrostatic pressure did not increase the blow formability of AZ31 sheet, even though it reduced the degree of cavitation. A possible reason for this behavior is discussed.

Development of Superplastic Forming/Diffusion Bonding Technology for Ti-6Al-4V Sandwich Panels (Ti-6Al-4V 샌드위치 패널제작을 위한 초소성/확산접합 기술개발)

  • Lee, Ho-Sung;Yoon, Jong-Hoon;Lee, Seung-Chul;Park, Dong-Kyu;Yi, Yeong-Moo
    • Journal of the Korea Institute of Military Science and Technology
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    • v.11 no.3
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    • pp.123-128
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    • 2008
  • Ti-6Al-4V alloy is a critical strategic metal used in aerospace structure due to the high specific strength, toughness, durability, low density, corrosion resistance. Examples of application of this alloy are airframe structural components, aircraft gas turbine disks and blades. Forming of this alloy is not easy due to its high strength and low formability. However, this alloy shows superplastic properties that allow for large plastic deformation under certain conditions. Combination of superplastic forming and diffusion bonding(SPF/DB) processes of this alloy has been widely used to replace mechanically fastened structures with reduced weight and fabrication costs. In this study, superplastic forming/diffusion bonding technology has been developed for fabricating lightweight sandwich panels with Ti-6Al-4V alloy. The experimental results show the forming of titanium lightweight sandwich structure is successfully performed from 3 and 4 sheets of Ti-6Al-4V.

3-D Finite Element Analysis of Superplastic Blow Forming (초소성재료의 압력성형에 관한 삼차원 유한요소해석)

  • Lee, Ki-Seok;Huh, Hoon
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.55-63
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    • 1994
  • The analysis of superplastic sheet forming process is studied by the use of the finite element method using a convected coordinate system and a skew boundary condition. In the formulation, the large inelastic behavior of the superplastic material is described as incompressible, nonlinear, viscous flow. The formulation is then approximated to the finite dimensional space with the use of membrane elements, which results in algebraic linear equations. In addition to the finite element formulation, a pressure cycle control algorithm is combined in the analysis for optimization of the forming time, which deals with the maximization of the strain rate sensitivity, the protection of the thickness reduction, the consistency of the desired strain rate and improvement of formability.

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Superplasticity of Magnesium Alloys and SPF Applications (마그네슘합금의 초소성 특성과 응용)

  • Shim, Jae-Dong;Byun, Ji-Young
    • Korean Journal of Materials Research
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    • v.27 no.1
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    • pp.53-61
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    • 2017
  • Magnesium alloys are of emerging interest in the automotive, aerospace and electronic industries due to their light weight, high specific strength, damping capacity, etc. However, practical applications are limited because magnesium alloys have poor formability at room temperature due to the lack of slip systems and the formation of basal texture, both of which characteristics are attributed to the hcp crystal structure. Fortunately, many magnesium alloys, even commercialized AZ or ZK series alloys, exhibit superplastic behavior and show very large tensile ductility, which means that these materials have potential application to superplastic forming (SPF) of magnesium alloy sheets. The SPF technique offers many advantages such as near net shaping, design flexibility, simple process and low die cost. Superplasticity occurs in materials having very small grain sizes of less than $10{\mu}m$ and these small grains in magnesium alloys can be achieved by thermomechanical treatment in conventional rolling or extrusion processes. Moreover, some coarse-grained magnesium alloys are reported to have superplasticity when grain refinement occurs through recrystallization during deformation in the initial stage. This report reviews the characteristics of superplastic magnesium alloys with high-strain rate and coarse grains. Finally, some examples of SPF application are suggested.

Nanostructured Bulk Ceramics (Part IV. Polymer Precursor Derived Nanoceramics)

  • Han, Young-Hwan;Mukherjee, Amiya K.
    • Journal of the Korean Ceramic Society
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    • v.47 no.3
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    • pp.205-209
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    • 2010
  • In the last (fourth) section, the discussion will entail a silicon-nitride/silicon-carbide nanocomposite, produced by pyrolysis of liquid polymer precursors, demonstrating one of the lowest creep rates reported so far in ceramics at the comparable temperature of $1400^{\circ}C$. This was first achieved by avoiding the oxynitride glass phase at the intergrain boundaries. One important factor in the processing of these nanocomposites was the use of the electrical field assisted sintering method.

A study on optimization of AZ31 alloy sheet by blow forming (AZ31 합금 부풀림 성형의 최적화 연구)

  • Kim, S.D.;Kwon, Y.N.;Lee, Y.S.;Kim, B.M.;Lee, J.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.67-69
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    • 2006
  • Since magnesium alloy has a limited formability at room temperature, forming should be carried out at the elevated temperature. If the initial grain size is small, superplasticity could be expected over $400^{\circ}C$. Using superplastic behavior, blow forming can be used to overcome the low formability of Mg alloys. In the present study, the optimization of blow forming of AZ31 alloy at the elevated temperature was investigated. Finite element simulation was carried out and verified with the blow forming experiments.

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