• Title/Summary/Keyword: thixoforming

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Post-heat Treatment Properties of Thixoformed of A357 Al Alloy Product (반응고 성형된 A357 Al 합금 성형품의 후열처리 특성)

  • Choi, W.H.;Shin, P.W.;Lee, S.Y.
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.1
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    • pp.16-25
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    • 2003
  • Recently, semi-solid forming (SSF) Process has been applied in many automobile parts for improved weight reduction, better environmental protection and energy savings. SSF process was well developed for high volume production of light weight aluminum components. In this paper, knuckle has been manufactured by SSF and then the microstructures and mechanical properties were investigated followed by various heat-treatment conditions. It was found that the examined microstructure was equiaxed at the whole cross-section area.

Continuous Fabrication Process of Rheology Material by Rotational Barrel Equipment (회전식 바렐 장치에 의한 레올로지 소재의 연속 제조 공정)

  • Seo P. K.;Jung Y. S.;Kang C. G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.10a
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    • pp.103-106
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    • 2004
  • The new rheology fabrication process has been developed to rheo die casting and rheo forming process. Thixoforming process has disadvantages in terms of induction reheating process, scrap recycling, loss of raw material and cycle time. Therefore, to reduce the number of process, new rheology fabrication process with specially designed the rotational barrel type equipment has been proposed to apply in various part productions. The barrel type equipment, which could continuously fabricate the rheology materil, was specially designed to have a function to control cooling rate, shear rate and temperature. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed. The barrel surface has both the induction heating system and the cooling system to control the temperature of molten metal. By using this system, the effect of the rotation speed and the rotation time on the microstructure was widely examined. The possibility for the rheoforming process was investigated with microstructural characteristic.

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Mechanical Characteristics Evaluation of Metal Matrix Composites Cylinder Linear Fabricated by Thixoforging Process (Thixoforging Process에 의하여 제조한 금속복합재료 실린더라이너 부품의 기계적 특성 평가)

  • 허재찬;이승후;강충길
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.2
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    • pp.58-65
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    • 2003
  • The conventional forming process such as squeeze casting or die casting for fabricating metal matrix composites products have a disadvantage such as non homogenous distribution of reinforcement, weak bonding between matrix and reinforcement and cost increase in parts fabrication. Thixoforming process has been accepted as a new method for fabricating the net shaped metal matrix composites with lightweight and wear resistance. In this paper, the effect of volume fraction and reinforcement sizes on mechanical properties in cylinder liner part of metal matrix composites has been investigated with processes parameters such as pressure and velocity. Moreover, the methods to obtain the thixoforged composites cylinder liner with high quality has been proposed. To evaluate the composites cylinder linear fabricated at the conditions proposed in this study, mechanical properties of fabricated composites cylinder linear were compared with those of commercial composites cylinder linear.

Microstructural Evolution of Electromagnetically Stirred Al alloy Billet During Isothermal Reheating at the Solid-liquid State (전자기 교반한 알루미늄합금 빌렛의 재가열시 고액공존구역에서의 조직변화)

  • Lee, Dock-Young
    • Journal of Korea Foundry Society
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    • v.28 no.3
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    • pp.129-135
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    • 2008
  • The reheating stage of electromagnetically stirred Al billet is a critical factor in the thixoforming process. When reheated to the solid-liquid state, the microstructure evolves to a more globular and more homogeneous structure by a coarsening mechanism, the kinetics depending on the initial microstructure. Microstructural evolution has been characterized by conventional parameters (mean size of particle and shape factor) as a function of holding time in the solid-liquid state. The aim of this study is to report experimental results concerning microstructural evolution in the solid-liquid state of electromagnetically stirred Al billet. The material was elaborated in the form of continuously cast bars solidified with electromagnetic stirring to degenerate the dendritic structure. The choice of the reheating conditions is determined by a dendritic ripening and coalescence mechanism, involving variations of both the shape and size of the particles. The reheating time has to be long enough to allow a minimum degree of spheroidizing, but has to be limited as much as possible in order to avoid excessive ripening. The optimum microstructure was obtained at the reheating temperature of near $584^{\circ}C$ and the holding time of 5 min. The only means of combining high productivity with good casting quality was to use feedstock billets whose microstructure showed rapid transformation characteristics.

Investigation of Reinforced Distribution in Fabrication Process of Metal Matrix Composites by Combined Stirring Process (복합교반법에 의한 금속복합재료의 제조공정에 따른 강화재의 분산성 검토)

  • 이동건;강충길
    • Composites Research
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    • v.14 no.5
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    • pp.1-11
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    • 2001
  • The particulates reinforced metal matrix composites(PMMC) have a number of interesting mechanical properties. including high strength and good resistance to wear at high temperature and low thermal expansion. The equipment structure to obtain the homogeneous distribution in composites are proposed for the continuous pouring of reinforcement at the desired temperature. The particulates reinforced metal matrix composites(A357/SiCp) were fabricated by the process of the combined stirring method with the various fabrication process. The combined stirring method to niform distribution of particle is consisted of two stirring force both electro-magnetic stirring generated from induction heating and mechanical stirring with graphite stirrer. PMMC billets were fabricated with the volume fractions ranged from 0% to 20% and particle sizes ranged from 14${\mu}{\textrm}{m}$ to 25${\mu}{\textrm}{m}$. It is important to cont the size of primary $\alpha$-Al solid particles because it could become the cause of the particle pushing or capture phenomena from the fact that secondary dendrite arm spacing size depends on the cooling rate during the solidification in hypoeutectic Al-Si alloy. Therefore, the effect of primary $\alpha$-Al on the reinforcement distribution in matrix alloys has been investigated. The microstructure of PMMC fabracated with various volume fractions(0%, 10%, and 20%) and particle size were observed.

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Tensile Properties of Thixoformed Semi-solid A356 Alloy (반용융 성형된 반응고 A356 합금의 인장 특성)

  • Yu, Yeong-Bin;Song, Pal-Yong;Kim, Sang-Sik;Lee, Jae-Hyeon;Lee, Myeong-Ho
    • Korean Journal of Materials Research
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    • v.10 no.1
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    • pp.69-76
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    • 2000
  • Despite the improved formability and processing advantages, the use of semi-solid metals is greatly limited due to the difficulties in controlling the optimum forming parameters. In the present study, the tensile properties of closed die, pressure formed semi-solid A356 alloy were examined. It was demonstrated that the tensile strength of thixoformed A356 alloy could be greatly reduced when the forming parameters were not rigorously controlled. The reduced strength of unappropriately formed products appeared to be related to the coarsening of the primary phases. The possibility of improving tensile properties of as-formed products by simple post heat treatment was also assessed.

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