• Title/Summary/Keyword: Semi-solid Aluminum Alloys

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Microstructures and Deformation Behavior of AA 2014 Aluminum Alloys in the Semi-Solid State (AA 2014 알루미늄 합금의 고상율에 따른 미세조직 및 반응고 변형 거동)

  • Han, Do-Suck
    • Journal of Korea Foundry Society
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    • v.37 no.5
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    • pp.157-163
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    • 2017
  • In the present study, the microstructural evolution and deformation behavior of AA 2014 aluminum alloys with different microstructures in a semi-solid state were investigated. For a given alloy, applied load and deformation time, the measured strain was higher at a higher temperature, indicative of a lower solid fraction. When a large proportion of the liquid was present as intragranular droplets, the alloy would not as easily deform because the effective liquid fraction between the solid grains had decreased. Greater deformation was achieved with higher grain boundary misorientations due to the enhanced wetting of the grain boundaries with liquid. A semi-empirical constitutive model is proposed for semi-solid deformation under the conditions in the present study. The mechanism of semi-solid deformation incorporates the initial flow of the liquid in the early stages of deformation, followed by a more gradual increase in the strain due to deformation by grain sliding accompanied by self-diffusion in the solid grains.

The Effect of Strain Rate on Macroscopic Behaviour in Compression Forming of Semi-Solid Aluminum Alloy (반용융 알루미늄 재료의 압축성형시 변형율속도가 미시적 거동에 미치는 영향)

  • 강충길;김기훈
    • Transactions of Materials Processing
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    • v.6 no.4
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    • pp.338-345
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    • 1997
  • The behaviour of alloys in the semi-solid state strongly depends on the imposed stress stage and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for material behaviour for variation of strain rate. Therefore, to investigate the effect of compression speed on deformation of aluminum alloy with globular microstructure, the compression test for semi-solid aluminum alloy with controlled solid fraction is perform by material test system which is attracted with furance. The behavior of semi-solid aluminum alloy were discussed for the various solid fraction and die speed. The material constants in stress-strain were are also proposed.

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Thixoforging Process of Rheology Materials fabricated by Spiral Mechanical Stirring (나선형 기계 교반 레오로지 소재의 이용한 Thixoforging 공정)

  • Han, S.H.;Jung, I.K.;Bae, J.W.;Kang, C.G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.05a
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    • pp.131-134
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    • 2007
  • A semi-solid forming technology has a lot of advantages compared to the die casting, squeeze casting and hot/cold forging, so semi-solid forming has been studied actively. Semi-solid forming has two methods. One is thixoforming with reheating of prepared billet, the other is rheoforming with cooled melt until semi-solid state. Thixoforging technology can produce non-dendritic alloys for semi-solid forming complex shaped parts in metal alloys. In this study, the thixoforging was experimented with made rheology materials by the spiral stirrer equipment. Rheology materials for forging were made by A356 casting aluminum alloy and A6061 wrought aluminum alloy. After experiment, forged samples were measured microstructure and were heat treated for high mechanical properties.

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The Effect of Electromagnetic Stirring on the Semi-Solid Microstructure of Cu-0.15wt%Zr Alloy (전자교반에 의한 Cu-0.5wt%Zr 합금의 반응고 조직제어에 관한 연구)

  • Lim, Sung-Chul;Lee, Heung-Bok;Kim, Kyung-Hoon;Kwon, Hyuk-Chon;Yoon, Eui-Pak
    • Journal of Korea Foundry Society
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    • v.26 no.1
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    • pp.40-45
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    • 2006
  • Most of the work reported concerned the semi-solid processing of low melting point alloys, and in particular light alloys of aluminum and magnesium. The purpose of this paper is to develop a semi-solid microstructure of Cu alloys using electromagnetic stirring applicable for squirrel cage rotor of induction motor. The size of primary solid particle and the degree of sphericity as a function of the variation in cooling rate, stirring speed, and holding time were observed. By applying electromagnetic stirring, primary solid particles became finer and rounder relative to as-cast sample. As the input frequency increased from 30 to 40 Hz, particle size decreased. The size of primary solid particle was found to be decreased with increasing cooling rate. Also, it decreased with stirring up to 3 minutes but increased above that point. The degree of sphericity became closer to be 1 with hold time. Semi-solid microstructure of Cu alloys, one of the high melting point alloys, could be controlled by electromagnetic stirring.

Microstructure and Formability of Semi-solid A390 Alloys made by uniform heating (균일가열법으로 제조한 반용융 A390합금의 미세조직 및 성형성)

  • 엄정필;장동훈;김득규;윤병은;임수근
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1997.06a
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    • pp.160-173
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    • 1997
  • Microstructure of hypereutectic Al-17wt.% Si alloy, fabricated by mechanical stirring and by reheating at semi-solid state, was investigated by optical microscope. Flow behavior semi-solid metal also was investigated at diffentent mould temperatures 280$^{\circ}C$, 290$^{\circ}C$ and 300$^{\circ}C$. Size of silicon particles were increased over 100$\mu\textrm{m}$ during solidification as a result of stirring. It is considered as microstructural coarsening by bonding between neighbouring primary silion particles during stirring of slurry. In case of reheating at semi-solid state, however, primary silicon particle was not increased at size of 40$\mu\textrm{m}$ and nearly spherical aluminum solde particle also could be obtained uniformly in distribution. The fludity of Al-17wt.% Si alloys at semi-solid state was improved when solid fraction was 0.7 at mould temperature of 300$^{\circ}C$ than other conditions.

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Thixo-extrusion of Semi Solid 7075 Aluminum Alloys and Mechanical Properties of The Extrudates (반응고 7075 알루미늄 합금의 반용융 압출 및 압출재의 기계적 특성)

  • Choi, Tae-Young;Kim, Dae-Hwan;Kim, Soo-Bae;Shim, Sung-Young;Lim, Su-Gun
    • Journal of Korea Foundry Society
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    • v.34 no.3
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    • pp.87-93
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    • 2014
  • Thixo-extrusion of semi-solid 7075 aluminum alloy and the mechanical properties of its extrudates were investigated. The semisolid alloy was prepared by a cooling slope cast. In other to perform thixo-extrusion, semi-solid 7075 aluminum alloy billets were reheated at the reheating conditions reported in a previous study. The maximum extrusion pressure in thixo-extrusion was 615MPa. This was lower than that of conventional hot extrusion ($P_{max}=940MPa$) at the same extrusion conditions due to the increased fluidity of the alloy billet in the semi-solid state. The values of Rockwell hardness (scale B) at the extrusion direction of the as thixoextruded bar were 48~53HRB and the difference in Rockwell hardness between the transverse direction and the extrusion direction was 5HRB or less. The results show that thxio-extrusion of semi-solid 7075 Al alloy improves the workability and anisotropic with the extrusion direction compared with hot extrusion of the conventional alloy.

Analysis of A356 alloys filling behavior considering Two-Phase flow (Two-Phase Flow를 이용한 A356 합금의 충전거동 해석)

  • Seol, D.E.;Kang, C.G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2006.05a
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    • pp.425-428
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    • 2006
  • A semi-solid forming technology has some advantages compared with conventional forming processes such as die casting, squeeze casting and hot/cold forging. In this study, the numerical analysis of semi-solid filling has been studied with solid fraction fs = 30% of A356 aluminum alloys. The finite difference program of two-phase flow model of Navier Stokes' equation coupled with heat transfer and solidification has been developed to predict a filling pattern, liquid segregation and temperature distribution of semi-solid metals. It gives die filling patterns and final solidification area. It can predict mechanical properties of semi-solid forming processes.

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The Effect of Plunger Tip Shape on the Formability in Semi-Solid Die Casting Process (반용융 다이캐스팅 공정에 있어서 플런저 팁의 형상이 성형성에 미치는 영향)

  • 서판기;손영익;강충길
    • Transactions of Materials Processing
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    • v.11 no.4
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    • pp.312-322
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    • 2002
  • In this study, an innovative semi-solid die casting technology to replace heavier cast iron compressor parts with lightweight aluminum castings was proposed, and the application possibility for home-appliance component was investigated. The most important factors regarding the semi-solid die casting process are the reheating process of the raw materials to the semi-solid state, specifications of the forming machine, the optimal injection conditions and die design. Materials used in this study were A3S7 and hSn alloys fabricated by the electromagnetic stirring process. The optimal injection conditions for semi-solid die casting process were Presented with the reheating conditions of the semi-solid materials. To investigate the effect of plunger tip shape on the formability and mechanical properties in semi-solid die casting process for complicated shape part, two kinds of plunger tip shape with long and short plunger tip taper are proposed.

Deformation Analysis of Semi-Solid Aluminum Material Considering Seperation Phenomena of Solid Particles (고상입자의 분리현상을 고려한 Semi-Solid 알루미늄재료의 변형해석)

  • 최진석;강충길;김기훈
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1997.03a
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    • pp.98-105
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    • 1997
  • The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can very from dendritic to globular. The estimation of behaviour characteristic in the compression simulation with seim-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for compression process is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process considering soldification phenomena is performed to the isothermal conditions of two dimensional problems. To analysis of compression process by using semi-solid materials, a new stress-strain relationship is described, and compression analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for compression force and ram displacement will be compared to experimental data.

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