• Journal of Korea Foundry Society
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• v.32 no.3
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• pp.127-132
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• 2012

Al-Zn-Mg alloys, being high strength aluminum alloys, have attracted attention as a material of automobile parts that require higher mechanical properties and lightness. Automobile parts with complex shapes are manufactured by low-priced casting method, but Al-Zn-Mg alloys are difficult to cast because of its poor hot cracking, feeding, and fluidity. Thus fluidity experiments on Al-Zn-Mg alloys were conducted for the castability evaluation. The effects of Mg and Zn, representative elements of Al-Zn-Mg alloys, on fluidity were observed. Spiral mold was used for fluidity experiments and the lengths of solidified specimens were measured after melting and gravity casting. Correlation between microstructures and fluidity length based on the alloy composition was considered. According to the experimental results, as the amount of Mg and Zn increased, fluidity decreased. Also, it was confirmed that fluidity change by the variation of Mg composition was greater than that of Zn.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.1-8
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• 1999

This study has investigated the effect of aging treatment on the microstructure and mechanical properties of Mg-6Al-xZn(x = 1.5, 2.5) alloys fabricated by the squeeze casting process. The microstructures of as-squeeze cast were composed of pro-eutectic ${\alpha}$, super saturated ${\alpha}$ and ${\beta}(Mg_{17}Al_{12})$ compound. Aged at both $200^{\circ}C$ and $240^{\circ}C$, Mg-6Al-xZn alloys showed the peak hardness due to the formation of ${\beta}(Mg_{17}Al_{12})$ precipitates. The discontinuous precipitates of the lamella type are predominant at $200^{\circ}C$ aging treatment, while the finely dispersed continuous precipitates were dominant at $240^{\circ}C$ aging treatment. Mg-6Al-xZn alloys fabricated by the squeeze casting process had the better combination of tensile strength and elongation compared to the conventionally cast alloys. As zinc contents increased, the tensile strength was increased by the solid solution strengthening effect of zinc.

• Journal of the Korean Ceramic Society
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• v.35 no.7
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• pp.685-690
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• 1998

The wetting behavior and the characteristic of spontaneous infiltration of pure Al and Al-(Si)-Mg alloys on {{{{ { {Al }_{ 2} O}_{3 } }} in vacuum argon and nitrogen atmosphere were investigated to find out the spontaneous in-filtration mechanism. The wetting of molten Al and Al alloys on {{{{ { {Al }_{ 2} O}_{3 } }} was only possible in cacuum at-mosphere but the sponataneous infiltration of molten Al-(Si)-Mg alloys was successfully made on {{{{ { {Al }_{ 2} O}_{3 } }} pre-form in nitrogen atmoshpere. The difference of wettability and spontaneous infiltration of molten Al and Al alloys on {{{{ { {Al }_{ 2} O}_{3 } }} were found to be related to formation of the Mg-N compound coated layer on {{{{ { {Al }_{ 2} O}_{3 } }} particles which was believd to increase wettability of molten Al alloys on {{{{ { {Al }_{ 2} O}_{3 }.

• Journal of Korea Foundry Society
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• v.17 no.3
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• pp.267-275
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• 1997

Fabrication of high strength Mg-Li-Al alloys by squeeze casting was established by the stabilization of melt and mold temperatures, applied pressure and the refining method. The entrapment of inclusions during pouring was prevented using 30 ppi alumina foam filter. The as-cast microstructure consists of a mixture of ${\alpha}$ and ${\beta}$ phases including AILi and $MgLi_2$, Al particles, which are distributed in the ${\beta}$ matrix. The grain sizes of gravity and squeeze casting alloys were 288 ${\mu}m$ and 207 ${\mu}m$ respectively. The addition of Al in Mg-Li alloys promoted the formation of second phase particles, which were adjusted to optimize the properties of Mg-Li-Al alloys. The Mg-10wt%Li-5wt%Al alloy after heat treatment at $350^{\circ}C$ for 1 hour showed the maximum hardness value. This is due to the facts that the amounts of ${\alpha}$ and ${\beta}$ phases and their distributions are dependent upon the solution treatment temperature, and that the amounts of AILi and $MgLi_2Al$ particles are dependent upon the Al content.

• Journal of Korea Foundry Society
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• v.34 no.6
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• pp.194-199
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• 2014

The effect of $Al_2Ca$ on the oxidation resistance and tensile property of Al-5Mg alloys was investigated. According to the TGA (Thermogravimetric analysis) result at $550^{\circ}C$ after 24hrs, the Al-5Mg alloy showed parabolic behavior with weight gain. On the other hand, there was almost no difference in the weight changes of the $Al_2Ca$ added Al-5Mg alloys during the oxidation. It was thought that the improvement of oxidation resistance in $Al_2Ca$ added Al-5Mg alloys might be due to the formation of a protective oxide layer with CaO and MgO on the surface. The microstructures of the alloys showed grain refinement with an increasing $Al_2Ca$ content. From the tensile test, the yield strength of the alloys were improved with an increasing $Al_2Ca$ content. The 0.07 mass%$Al_2Ca$ added Al-5Mg alloy showed similar elongation and increased strength, simultaneously. It was considered that the addition of $Al_2Ca$, which was superior in the oxidation resistance of Al, reduced the formation of Mg oxides and inclusions during the alloying. This, partly led to the improvement of tensile properties.

• Journal of Powder Materials
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• v.29 no.3
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• pp.233-239
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• 2022

Aluminum alloys are extensively employed in several industries, such as automobile, aerospace, and architecture, owing to their high specific strength and electrical and thermal conductivities. However, to meet the rising industrial demands, aluminum alloys must be designed with both excellent mechanical and thermal properties. Computer-aided alloy design is emerging as a technique for developing novel alloys to overcome these trade-off properties. Thus, the development of a new experimental method for designing alloys with high-throughput confirmation is gaining focus. A new approach that rapidly manufactures aluminum alloys with different compositions is required in the alloy design process. This study proposes a combined approach to rapidly investigate the relationship between the microstructure and properties of aluminum alloys using a direct energy deposition system with a dual-nozzle metal 3D printing process. Two types of aluminum alloy powders (Al-4.99Si-1.05Cu-0.47Mg and Al-7Mg) are employed for the 3D printing-based combined method. Nine types of Al-Si-Cu-Mg alloys are manufactured using the combined method, and the relationship between their microstructures and properties is examined.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.86-90
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• 2012

Aluminium-silicon based casting alloys have received an attention for high electrical and thermal conductivity applications, however relatively low conductivity of Al-Si alloys often limits the application. Efforts have been made to develop new high conductivity aluminium casting alloys containing no or less silicon. In this study Al-Zn-Fe based alloys were selected as the new alloys, and the effect of Mg additions on their properties and casting characteristics were investigated. As the magnesium content was increased, the tensile strength of Al-2Zn-0.2Fe based alloy was remarkably increased, while the electrical conductivity was deteriorated. It was observed that the fluidity of the alloys was generally inversely proportional to the Mg content but the hot cracking resistance was rather proportional to it. Cooling curve analyses were carried out to measure the actual solidification range and dendrite coherency temperature.

• Journal of Korea Foundry Society
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• v.31 no.5
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• pp.293-301
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• 2011

Representative magnesium alloys applied to the die-casting are AZ91, AM60, etc., and the application of these alloys is restricted to components operating at moderate temperatures, due to grain boundary siding of ${\beta}$-phase($Mg_{17}Al_{12}$) at temperatures above $120^{\circ}C$. Heat-resistant magnesium alloys such as AE42, AE44 have been developed, but that have been too burdensome to produce because of the expensive rare earth materials. Research work for the development of low-priced heat-resistant magnesium alloy is actively in progress and positive results are being reported. This study aims to investigate the effect of Ca additions on mechanical properties of Mg-4Al-2Sn heat resistant magnesium alloys. Mg-4Al-2Sn alloys with Ca (0wt.%, 0.3wt.%, 0.7wt.%, 1wt.%) have been produced through the die-casting process for the development of low-priced heat-resistant magnesium alloy, and high temperature tensile tests are performed using the specimens. The results showed that mechanical properties of Mg-4Al-2Sn-xCa increased with the addition of Ca up to 0.7wt.% Ca and further addition of Ca deteriorated the mechanical properties of the alloys. A significant amount of porosity was observed at the sample with 1wt%. Ca and the longer freezing range of the alloy was believed to cause the formation of porosity.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.975-980
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• 2003

The electrochemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH)₂ in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH)₂ was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the β phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in β phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in α phase, which had a lower Al content. In the anodic polarization test in 0.017 mol·$dm^{-3}$ NaCl and 0.1 mol·$dm^{-3}$ Na₂SO₄ at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the α phase is a non-compacted film. The anodic film on the α phase at 30 min was a compact film as compared with that at 10 min.

• Journal of Korea Foundry Society
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• v.24 no.6
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• pp.340-346
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• 2004

The plan for obtaining a good combination of strength and castability appeared feasible and the following observations were made. 1. In Al-12Mg-6.6Zn-xSi alloys, more primary $Mg_2Si$ phase formed with reduced $Al_3Mg_2$ phase, as Si content is necessary for an effective solution heat treatment because the solidus temperature is very low silicon contents. 2. A high tensile strength could be obtained in the heat-treated Al-12Mg-5.5Zn-5Si alloy attributed in the heat-treated Al-12Mg-5.5Zn-5Si alloy attributes to fine $MgZn_2$ particles that precipitated uniformly in the matrix. 3. Al-12Mg-5.5Zn-Si alloys showed excellent casting capabilities such as hot cracking resistance and fluidity compared to the reference commercial alloys. 4. The wear resistance of Al-12Mg-5.5Zn-5Si alloy was superior to that of A7075 alloy, and even higher resistance is expected if the morphology and size of primary $Mg_2Si$ phase is carefully controlled.