• Journal of Korea Foundry Society
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• v.39 no.5
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• pp.94-101
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• 2019

This study investigated the microstructure properties of A356 and AC8A alloys with a rheocasting mold using an inclined cooling plate. In addition, a formability evaluation was performed according to the solid fraction. Regardless of the position, the overall microstructure was shown to be uniform and a finer crystal structure was obtained as the solid fraction increased. The study confirmed that the molding pattern changed according to the solid fraction and that the spherical α-Al and eutectic α were identified. The results of the formability according to the solid fraction of A356 and AC8A alloys were similar to the simulation results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.975-981
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• 2017

Savings in weight using lightweight materials such as aluminum alloy can lead to increase fuel economy. However, compared to steel, aluminum alloys have a lower strength for an equivalent life cycle. To reduce the weight of automobiles, research is being performed on the fabrication of lighter and stronger torque struts without having to sacrifice the safety of automotive components. In this study, a weight reduction design process for torque struts is proposed that is based on varying von-Mises stress contours using an aluminum alloy (A356) having a tensile strength of 245 MPa, instead of STKM11A steels. The optimized design can reduce the weight of the original steel torque strut by over 42% and it can contribute to the design of light-weight components and to the safe design of torque struts.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.61-65
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• 2020

Rheo-diecasting with stirring has been used in many material industries. As the 4th Industrial Revolution approaches the world, eco-friendly high-strength and light-weight materials become more important. Casting methods have been studied and used for aluminum-alloy automobile parts. This study carried out the effect analysis of the micro-structure and mechanical properties, such as yield/ultimate tensile strength, elongation, and hardness, of A356 using the 6-pole EMS (electro-magnetic stirring) casting process with a high electromagnetic force. As a result, the hardness and elongation of the A356 after T6 heat-treatment show a significant improvement, respectively, by 20% and 50%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.355-358
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• 2004

In this study, the deformation characteristics of grain-size controlled rheology materials surfaces were investigated as a part of the research on the surface crack prediction in semi-solid formed automobile components. The microstructure of rheology Al-Si alloys consists of primary and eutectic regions. In eutectic regions the crack initiation begins with initial fracture of the eutectic silicon particles and inside other intermetallic phases. Nano-deformation characteristics in the eutectic and primary region of semi-solid aluminum alloys (356 alloy and 319 alloy) were investigated through the nanoindentation/scratch experiments and the AFM observation.

• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.94-100
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• 2004

Gas porosity which is a common defect in aluminum alloy casting, is also thought to be severer in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring. Fundamental experiments were carried out to evaluate the effect of process variables such as the melt treatment, the cooling rate and pouring temperature on the density and mechanical properties in A356.2 castings with simple bar shape. The density of grain refined specimen was slightly lower than that of degassed one, but was higher than that of no treated one and that of shot ball packed specimen was higher than the other specimens. The tensile strength and elongation were in the ranges of $200{\sim}230MPa$ and $0.5{\sim}1.5%$ respectively. The density and hardness of lost foam cast specimens decreased with increase in pouring temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.463-466
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• 2005

The microstructure and mechanical properties of rheocast A356 aluminum alloy by electromagnetic stirring are studied. In the electromagnetic stirring, main parameters are stirring current and stirring time. Stirring current is ranged from 0 A to 60 A, and stirring time is 20, 40, and 60 sec. In the rheocasting, injection velocity and applied pressure are changed. In this paper, the effect of stirring current and stirring time on the morphology and mechanical properties are investigated and analyzed.

• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.109-113
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• 2002

A good fluidity of high strength Al-alloys is required to cast thin wall castings needed to reduce the weight of cast parts. The fluidity, measured as the length to which the metal flows in a standard channel, is affected by many factors, such as the pouring temperature, solidification type of the alloy, the channel thickness, melt head, mold materials and temperature, coating etc. Therefore the experimentally measured fluidity scatters very much and makes it difficult to estimate the fluidity of a melt with a few measurements. The effect of Ti content and grain refinement on the fluidity of high strength aluminum alloy was investigated with a test casting with 8 thin flow channels to reduce the scattering of the fluidity results. The fluidity of Al-4.8%Cu-0.6%Mn Al-6.2%Zn-1.6%Mg-1.0%Cu and well-known commercial aluminum alloy, A356 was tested. Initial content of Ti was varied from 0 to 0.2wt% and Al-5Ti-B master alloy was added for grain refinement. The flow length varied linearly with superheat. By adding Ti and Al-5Ti-B, the fluidity increased. The grain size decreased by adding grain refiner at the same time. The fluidity depended on the degree of grain refinement. The fluidity of the alloy solidifying in mushy type is improved by grain refinement, because grain refinement increases the solid fraction at the time of flow stoppage.

• Journal of Korea Foundry Society
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• v.32 no.1
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• pp.24-31
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• 2012

In this study, semi-solid thin plate of A 356 aluminum alloy was fabricated by using slope plate apparatus and vacuum pressurization. Slope plate was used to produce semi-solid material with spheroidal microstructures. After molten metal was poured into the slope plate connected to the pouring hole of die, semi-solid material flowed into the die cavity by vacuum degree. The primary crystals of the cast metal became spheroidal. In order to increase the working pressure, gas pressurization of U shape was designed for fabrication of thin plate. For 3 bar of gas pressure and 60 mmHg of vacuum degree, thin plate was fabricated without defects on surface.

• Transactions of Materials Processing
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• v.5 no.3
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• pp.239-255
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• 1996

A new forming technology has been developed to fabricate near-net shape products using light metal. A semi-solid forming technology has some advantages compared with the conventional forming processes such as die casting squeeze casting and hot/cold forging. In this study the numerical analysis of semi-solid filling for a straight die shape and orifice die shape in gate pattern is studied on semi-solid materials(SSM) of solid fraction fs =30% in A356 aluminum alloy. The finite difference program of Navier-Stokes equation coupled with heat transfer and solidification has been developed to predict a filling pattern and the temperature distribution of SSM. The programdeveloped in this study gives die filling patterns of SSM and final solidifica-tion region.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.81-88
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• 2012

Turbopump is a key component in liquid rocket engines, and reducing weight while maintaining structural safety is one of the major concerns of turbopump designers. To reduce the weight aluminium alloy castings instead of steel casings are introduced. The casting process is especially useful for enhancement of productivity and for reduction of product costs. But, since castings are used in space vehicle engines, reliability cannot be compromised. Therefore, proper design, production process and thorough investigation should be performed to ensure structural integrity. In this study inlet casings for a fuel pump were casted with A356.0-T6 alloy and using one of them a burst test was conducted to ensure structural integrity. Structural analysis is performed for simulation, and with multiple strain gages strains are measured and compared with predictions.