• Journal of Korea Foundry Society
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• v.30 no.6
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• pp.205-209
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• 2010

This study evaluates the influence of strontium addition and holding time on mechanical properties for Al-10.5wt%Si-2wt%Cu secondary die-casting alloy and the measured electrical conductivity of modified alloys. A general improvement in the mechanical properties of the alloy was observed after adding the strontium. Ultimate tensile strength, elongation and electrical conductivity of modified alloys were improved by increasing strontium content and holding time. From these results, the optimal strontium content and holding time were identified on the mechanical properties of Al-10.5wt%Si-2wt%Cu secondary die-casting alloys.

• Journal of Korea Foundry Society
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• v.41 no.2
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• pp.127-131
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• 2021

Based on its good compatibility with high-temperature environments, the Ti-48Al-2Cr-2Nb alloy is used for high-temperature materials of industrial equipment. In this study, a Ti-48Al-2Cr-2Nb alloy turbocharger turbine wheel was fabricated by a vacuum centrifugal casting method. The conditions that prevent misrun defects of the turbocharger turbine wheel blade from centrifugal casting using alumina molds were investigated. The microstructure of the alloy prepared by vacuum centrifugal casting was studied by means of optical microscopy (OM), with a micro-Vickers hardness analyzer (HV), by X-ray diffraction (XRD) and by SEM-EDS. The HV and SEM-EDS examinations of the as-cast Ti-48Al-2Cr-2Nb alloy showed that the thickness of the oxide layer (α-case) was typically less than 50 ㎛. At a high preheating temperature of 1,100℃, a moderate RPM of 260, and with an alumina mold with a large gate size, there were almost no misrun defects. Therefore, it was confirmed that a Ti-48Al-2Cr-2Nb alloy turbocharger turbine wheel with fewer misrun defects could be achieved through a high preheating temperature, a moderate RPM, a large gate size and an alumina mold to suppress the formation of alpha-case components.

• Journal of Korea Foundry Society
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• v.41 no.1
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• pp.3-10
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• 2021

In the compound casting between the aluminum alloy and the cast iron, the iron component may be dissolved from the cast iron during the process and mixed into the aluminum melt, thereby forming various iron-containing intermetallic compounds and significantly deteriorating the tensile properties of the aluminum alloy. On the other hand, unlike Fe, which is added as an impurity, Cu is added to improve the mechanical properties of the aluminum alloy. In this study, the change in microstructure and tensile properties of aluminum alloys due to the addition of Fe and Cu was investigated. A large amount of iron-containing compounds such as coarse Al₅FeSi phases were formed when the iron content was 1% or more, and the tensile properties were significantly reduced. In the case of the aluminum alloy to which Cu was added, an Al₂Cu phase was additionally formed and the tensile strength was clearly improved.

• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.464-470
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• 1994

The horizontal continuous casting method with the heated mold was applied to study the solidification structures of the pure Al and Al-0.5wt%Si and Al-1.0wt%Si alloy rods. The results could be summarized as follows: 1. The S/L interface structures of pure Al represented the hexagonal cells at the casting speed of 590 and 350mm/min, respectively. However, the hexagonal cells became irregular as the casting speed and(or) Si amount increased. 2. The striation increased as the Si amount and casting speed increased and was found to result from the occurrence of growth twin crystals by XRD analysis. 3. The striation did not affect the mechanical and electrical property of the drawn wire from the casted rod. This means the striation is not a serious defect which has to consider in the production of micro-sized fine wire in the drawing process.

• Korean Journal of Metals and Materials
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• v.50 no.7
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• pp.531-538
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• 2012

In this study, we evaluated the fluidity of the Al-Zn based alloys which exhibit excellent mechanical properties. We conducted computer simulations of fluid flow using the results of DSC, DTA analysis and Java-based Materials Properties software (J. Mat. Pro). Such computer simulations were then compared with the results obtained from experimental observations. The computer simulation results and the experimental results were very similar in fluidity length. It was found that the fluidity length of Al-Zn alloys is improved by increasing the Zn content while decreasing the solidus temperature of an alloy. In addition, we elucidate the effect of Zn addition on variations in different mechanical properties and the microstructure characteristics of (Al-xZn3Cu0.4Si0.3Fe) x=20, 30, 40, and 45 wt% alloys fabricated by gravity casting.

• Journal of Korea Foundry Society
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• v.25 no.4
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• pp.156-160
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• 2005

There are many factors that influence solidification behavior during continuous casting, e.g. include superheat, casting speed, cooling rate and holding time. However, when melt is stirred by electromagnetic force, there would be some changes in its solidification behavior compared to that of the ordinary casting process. In this study, the billets of A356 alloy with a diameter of 3 inch were fabricated with electromagnetic stirring under various conditions of superheat, casting speed and input voltage of electro magnetic stirring (EMS) device. The microstructure was also investigated under the various casting conditions and electromagnetic input voltages. When increase in input voltage, the microstructure was changed from dendritic to rosette type and finally to spheroidal. With pouring temperature, casting speed and electromagnetic input voltage were $650^{\circ}C$, 100 mm/min and 140 V, respectively, the billet with a diameter of 3 inch, which has a uniform dispersed spheroidal particles in the whole area of billet except for the surface area, was manufactured.

• Journal of Korea Foundry Society
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• v.33 no.1
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• pp.22-31
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• 2013

In order to develop an aluminum alloy, that can combine high thermal conductivity and good castability and anodizability, aluminum alloys with low Si content, such as Al-(0.5~1.5)Mg-1Fe-0.5Si and Al-(1.0~1.5)Si-1Fe-1Zn, were designed. The developed aluminum alloys exhibited 170~190% thermal conductivity (160~180 W/mK), 60~85% fluidity, and equal or higher ultimate tensile strength compared with those of the ADC12 alloy. In each developed alloy system, the thermal conductivity decreased and the strength increased with the increment of Mg and Si, which are the significant alloying elements. The fluidity was in reverse proportion to the Mg content and in proportion to the Si content. The Al-(0.5~1.5)Mg-1Fe-0.5Si alloys exhibited better fluidity in thick-wall castings, while the Al-(1.0~1.5)Si-1Fe-1Zn alloys were better in thin-wall castability due to their lower surface energies. The fluidity behavior was complexly affected by the heat release for the solidification, viscosity, solidification range, and the type, quantity, and formation juncture of the main secondary phase.

• Journal of Korea Foundry Society
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• v.29 no.1
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• pp.27-32
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• 2009

The microstructure of Al-7Si-0.4Mg-1Fe alloy mainly consists of aluminum dendrites, Al-Si eutectics, and $Al_5FeSi$ needles. When Mn was added to the alloy, the substantial amount of $Al_5FeSi$ phase was changed into Al(Mn,Fe)Si, however the needle-like morphology was almost unchanged. Combined additions of Cr or Sr with Mn to the base alloy resulted in rod-like Al(Mn, Fe,Si)Si phase. The tensile properties of as-cast alloys were enhanced by the Mn addition, especially when it was added with Sr. The tensile properties after T6 heat treatment was a little improved with 0.7%Mn addition, but Cr or Sr additions with Mn didn't show any positive effect on the properties of heat-treated alloys.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.6
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• pp.359-366
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• 2023

Changes in microstructure and mechanical properties of Mg-1.0Al-1.0Zn-0.2Mn-0.5Ca (AZMX1100) alloy sheet manufactured by normal casting and twin roll casting process, were studied according to process and heat treatment. Non-uniform microstructure was observed in the initial sheet produced through both processes, and in particular, tilted dendrites and shifted central segregation were observed in the twin roll casting sheet. It was homogenized through hot rolling and heat treatment, and heat treated at 350℃ and 400℃ to compare the effect of heat treatment temperature. Both sheets were homogenized by the hot rolling process, and the grain size increased as the heat treatment temperature and time increased. It was confirmed that the grain size, deviation, and distribution of the second phase were finer and more homogenized in the TRC sheet. Accordingly, mechanical properties such as hardness, formability, and tensile strength also showed better values. However, unlike other previously reported AZMX alloy systems, it showed low formability (Erichsen value), which was judged by the influence of Al2Ca present in the microstructure.

• Journal of Korea Foundry Society
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• v.37 no.6
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• pp.186-192
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• 2017

The lost foam casting method was used to fabricate Al-Si alloy thin sheet specimens; the effects of chemical composition and process variables on the mold filling and mechanical properties were investigated. The mold filling capability was observed to be proportional to the pouring temperature, and both the vibration imposed during the casting and the application of a pattern coating had rather negative effects. The mold filling capability also decreased with the addition of Mg or TiB. When the Mg content increased, the tensile strength of the cast alloy was enhanced, but the elongation decreased. However, after T6 heat treatment, both the strength and the elongation were improved. TiB addition for grain refining or pattern coating did not significantly affect the tensile properties.