• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.70-73
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• 2003

Semi-solid processing is now becoming of great interest for the production of various parts by pressure die casting. Many advantages are associated with this forming process at the condition that the forming operation is performed under appropriate conditions in terms of alloy microstructure, injection velocity and pressure. In this study, to look into the relation along them, the experiment of semi-solid die casting has been peformed with various condition of injection, and investigated their microstrucure and solid fraction

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.178-184
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• 2000

To obtain high quality component with thixoforming process, it is important that the homegeneous distribution of solid particles without liquid segregation. In closed-die semi-solid forging process, liquid segregation is strongly affected by injection velocity than any other process variables because the material has to travel relatively long distance to fill the cavity through a narrow gate before solidification begins. The optimal injection velocity and die temperature were investigated to fabricate near-net-shape compressor component called Al frame.

• 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.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.258-259
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• 2006

New powder compaction process, in which a Bingham semi-solid/fluid mold is utilized, is developed to fabricate micro parts. In the present process, a powder material is filled as slurry in a solid wax mold, dried and compressed. The wax is heated during compaction and becomes semi-solid state, which can acts as a pressurized medium for isostatic compaction. Since the compacted micro parts are very fragile, the mold's temperature is controlled to higher than its melting point during unloading, to avoid breakage of the compacts. To demonstrate effectiveness of this process, some micro compacts of alumina are shown as examples.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.89-95
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• 1999

The compression behavior of semi-solid materials in studied from a viewpoint of yield criteria and analysis methods. To describe the behavior of materials in semi-solid state, several theories have been proposed by extending the concept of plasticity of porous compressible materials. in the present work, the upper-bound method and the finite element method are used to model the simple compression process using yield criteria of Kuhn and Doraivelu. Segregation between solid and liquid which cause defect of product is analysed for Sn-15%Pb alloy is compared with the experimental result of Charreyron et al..

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.29-35
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• 1996

For semi-solid forging with aluminuim alloys, it is required to develope the globular grain structure. It was studide that cold upsetting ration in SIMA process has effect on the globularization of grain structure. Globular microstructure was generated without cold upsettings for commercial aluminium alloys. In the case of A12024, the range of grain size was 40 .approx. 50 .mu. m. The grain growth in growth in globular microstructure depend on heating time. Spur gear was forged in semi-solid state to investigate the forging condition for A12024 with hydraulic press.

• Journal of Korea Foundry Society
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• v.15 no.2
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• pp.184-193
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• 1995

Effects of process parameters during thixocasting, such as solid volume fraction, mold temperature and extrusion ratio, on the mold filling behaviour and fluidity of Mg alloy(AZ91D) have been investigated. The semi-solid ingot held for 60 minutes at the semi-solid temperature range did not contain the equilibrium volume fraction of solid as expected from the phase diagram. Therefore, in order to obtain the desired solid fractions, and to suppress the exaggerated grain growth during heating, it was required to heat the ingot rapidly up to the temperature $10^{\circ}C$ higher than the semi-solid temperature suggested from the phase diagram for a specific volume fraction of solid. The experimental results show that mold filling behaviour and fluidity can be improved with the use of the higher mold temperature and the lower volume fraction of solid, but remain nearly unaffected by the change of extrusion ratio.

• 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.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.75-80
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• 2012

In this study, we are aimed to prevent grain growth of semi-solid AZ31 magnesium alloys during reheating process. The semi-solid AZ31+(Ca) billets were investigated by using metallographic analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy in order to elucidate the effect of Ca addition during reheating process. The grain growth of semi-solid AZ31+(Ca) billet was reduced with increasing Ca content during reheating. The grain size of AZ31+(Ca) billet decreased with increasing volume fraction of Al2Ca particles. The grain growth rate constant K calculated by Oswald ripening LSW theory in AZ31+1.5wt.% Ca billet was the lowest 129.

• Journal of Korea Foundry Society
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• v.29 no.6
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• pp.265-269
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• 2009

The optimum RRA heat treating conditions and SCC (stress corrosion cracking) resistance of semi-solid Al-Zn-Mg-Cu alloy fabricated by inclined cooling plate were compared with those of conventional mould cast alloys. The non-stirring method characterized by using a cooling plate can effectively eliminate dendritic structure and form a fine globular semisolid microstructure in as-cast Al-Zn-Mg-Cu alloy and the SCC resistance of semi-solid Al-Zn-Mg-Cu alloy was higher than that of conventional mold cast alloy. Also, after retrogressed treatment at RRA heat treatment of semi-solid Al-Zn-Mg-Cu alloy, retrogressed treatment time has increased more than 10 minutes at $180^{\circ}C$ to recovery the T6 heat treatment strength.