• Journal of Korea Foundry Society
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• v.21 no.6
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• pp.328-335
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• 2001

The objective of this study is to investigate on manufacturing Al-scrap into hypereutectic Al-Si alloy by using electromagnetic force. The Fe element in the aluminium scrap was controlled by intermetallic compound method and using EMF(electromagnetic force). The most lumped compound was found after 10min holding at $690^{\circ}C$. A number of segregated compound was revealed when imposed to EMF at 30A. The refinement of primary Si particles was achieved by EMF stirring. Primary Si particles were refined and spheroidized most of all with the magnetic intensity of 180G for 10 min.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.296-302
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• 2005

In order to improve mechanical properties, the hypereutectic Al-20 wt%Si based prealloy powder was prepared by gas atomization process. Microstructure and compressibility of the atomized Al-Si powder were investigated. The average powder size was decreased with increasing the atomization gas pressure. Size of primary Si particles of the as-atomized powder was about $5-8\;\mu{m}$. The as-atomized Al-Si powder such as AMB 2712 and AMB 7775 to increase compressibility and sinterability. Relative density of the mixed powder samples sintered at $600^{\circ}C$ was reached about 96% of a theoretical density.

• Journal of Powder Materials
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• v.15 no.2
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• pp.142-147
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• 2008

The hypereutectic Al-20 wt%Si powders including some amount of Cu, Fe, Mg, Mn were prepared by a gas atomization process. In order to get highly densified Al-Si bulk specimens, the as-atomized and sieved powders were extruded at $500^{\circ}C$, Microstructure and tensile properties of the extruded Al-Si alloys were investigated in this study. Relative density of the extruded samples was over 98%. Ultimate tensile strength (UTS) in stress-strain curves of the extruded powders increased after T6 heat treatments. Elongation of the samples was also increased from 1.4% to 3.2%. The fracture surfaces of the tested pieces showed a fine microstructure and the average grain size was about $1{\mu}m$.

• Metals and materials international
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• v.24 no.6
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• pp.1376-1385
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• 2018

Ultrasonic melt treatment (UST) was applied to an A390 hypereutectic Al-Si alloy in a temperature range of $750-800^{\circ}C$ and its influence on the solidification structure and the consequent increase in strength was investigated. UST at such a high temperature, which is about $100^{\circ}C$ above the liquidus temperature, had little effect on the grain refinement but enhanced the homogeneity of the microstructure with the uniform distribution of constituent phases (e.g. primary Si, ${\alpha}-Al$ and intermetallics) significantly refined. With the microstructural homogeneity, quantitative analysis confirmed that UST was found to suppress the formation of Cu-bearing phases, i.e., $Q-Al_5Cu_2Mg_8Si_6$, $Al_2Cu$ phases that form in the final stage of solidification while notably increasing the average Cu contents in the matrix from 1.29 to 2.06 wt%. A tensile test exhibits an increase in the yield strength of the as-cast alloy from 185 to 208 MPa, which is mainly associated with the solute increment within the matrix. The important role of UST in the microstructure evolution during solidification is discussed and the mechanism covering the microstructure-strengthening interrelationship of the ultrasonically treated A390 alloy is proposed.

• Journal of Korea Foundry Society
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• v.26 no.6
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• pp.241-248
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• 2006

The effects of silicon content and melt treatment on the fluidity of Al-Si alloys during squeeze casting were investigated. The fluidity of Al-3.0 wt%Si alloy was found to be lower than that of Al-1.0 wt%Si and the fluidity of the alloy with more than 3.0 wt%Si increased with the silicon content upto 13.0 wt% and rather decreased with15.0 wt%. The fluidity was also increased by the separated treatment of grain refinement or eutectic modification, and even more by the simultaneous treatment of both. The fluidity of hypereutectic alloy was increased by the refinement of primary silicon particle.

• Journal of Korea Foundry Society
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• v.20 no.2
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• pp.89-96
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• 2000

The effects of modification processing on the refinement of primary Si and the wear behavior of hyper-eutectic Al-Si alloys have been mainly investigated. Refining effects of primary Si in Al-17%Si alloy was more efficient than that of B.390 alloy. Optimum condition of getting the finest primary Si microstructure was when AlCuP modifier is added into the melt at $750^{\circ}C$ and held it at $700^{\circ}C$ for 30 minutes. Wear loss in the specimens of as-cast condition decreases as the size of primary Si decreases, in the order of B.390 alloy, B.390 alloy with AlCuP addition, Al-17%Si alloy and Al-17%Si alloy with AlCuP addition. Wear loss in the aged condition of Al-17%Si alloy, B.390 alloy and B.390 alloy with AlCuP addition decreased due to the increase of compressive residual stress in the matrix by the aging treatment. While, wear loss increased in the aged specimens of Al-17%Si alloy with AlCuP addition and Hepworth addition in which compressive residual stress decreases by the aging treatment. Therefore, it is assumed that higher compressive residual stress in the matrix can reduce the wear loss in composite materials such as hyper-eutectic Al-Si alloys.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.4
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• pp.244-252
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• 1994

The morphological changes of primary solid particles as a fuction of process time on Al-Si alloys during semi-solid state processing with a shear rate of 200s were studied. In hypereutectic Al-15.5wt%Si alloy, it was observed that primary Si crystals are fragmented in the early stage of stirring and morphologies of primary Si crystals change from faceted to spherical during isothermal shearing for 60 minutes. In quaternary Al-12.5wt%Si-2.9wt%Cu-0.7wt%Mg alloy system, it was observed both primary silicon and ${\alpha}$-alumunum particles. Microstructural evolution of primary Si crystals was similar to that of the hypereutectic Al-Si alloy but equiaxed ${\alpha}$-Al dendrites are broken into nearly spherical at the early stage of shearing and later stage of the isothermal shearing ${\alpha}$- Al particles are slightly coarsoned by Ostwald ripening. Mechanical properties of Al-Si-Cu-Mg alloy were compared to those from other processes (squeeze casting and gravity casting). After T6 heat treatment, comparable values of hardness were obtained while slightly lower compressive strength values were observed in rheocast alloy. The elongation, on the other hand, exhibited significant increasement of 15% over gravity cast alloy.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.311-318
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• 1997

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.483-493
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• 1995

The microstructural changes during semi-solid state processing of hypereutectic Al-Si alloy has been investigated in the present study. Stirring of semi-solid slurry results in the morphological changes of the primary Si particles, i.e. from angular rod shape to near-spherical shape. Besides the spherodization of primary Si particles, the average particle size increases, especially, at much higher rate in the final stage than that in the early stage of stirring. Various microstructure characterization techniques, such as anisotropic etching, SEM imaging and ECP analysis, reveal that the spherodization of primary Si particles occurs by the combinations of the mechanisms of coalescence, fracture, and wear of the individual particles. Isothermal shearing of hypereutectic Al-Si at $580^{\circ}C$ shows that spherical ${\alpha}-Al$ particles are formed by the dissociation of Al-Si eutectic structure at the early stage of isothermal shearing. The spherical ${\alpha}-Al$ particles gradually grow by the mechanisms of Ostwald ripening and coalescence of the particles.

• Journal of Korea Foundry Society
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• v.43 no.6
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• pp.294-301
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• 2023

The effects of Cu on feeding and macro-porosity characteristics were investigated in hypo- (A356 and 319) and hypereutectic (391) aluminum-silicon alloys. T-section and Tatur tests showed that the feeding and macro-porosity characteristics were significantly different between the hypo- and hypereutectic alloys. The hole and the pipe in the T-section and the Tatur casting in hypereutectic alloy showed a rough and irregular shape due to the faceted growth of the primary silicon, while the results of the hypoeutectic alloys exhibited a rather smooth surface. However, the addition of Cu did not strongly affect the macro-feeding behavior. It is known that copper segregates and interferes the feeding process in the last stage of solidification, possibly leading to form more amount of micro shrinkage porosity by the addition of Cu. The macro porosity formation mechanism and feeding properties were discussed upon T-section and Tatur tests together with an alloying addition.