• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.77-83
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• 2002

Magnesium alloys casting are gaining increased acceptance in the automotive and electronic industeries and die casting is the most efficient method of manufacturing such mass produced parts. This study has been investigated the microstructures and mechanical properties of Mg-9Al-lZn alloy fabricated by die casting process for development of air bag case. The microstructure of die casted specimen were composed of pro-eutectic magnesium solid solution and $\beta$(Mg17Al12) precipitates. The tensile strength of as-fabricated Mg-9Al-lZn alloy revealed 231.4MPa. It was found that Mg-9Al-lZn alloy have good corrosion resistance in electrochemical polarization test.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.63-70
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• 2001

The solidification cracking susceptibilities of Al-Mg alloy laser welds were assessed using self-restraint tapered specimen crack test. The dependence of cracking susceptibility of Al-Mg alloy laser welds on Mg contents was observed to be similar to that of arc welds in the same materials. The cracking susceptibility of Al-Mg alloy laser welds increased as Mg content increased up to 1.6-1.9 wt.% and then it decreased as Mg content increased further. The peak cracking susceptibility occurred at around 1.6 to 1.9 wt.% Mg for both autogenous and wire feed welds. It was also observed that the cracking susceptibility decreased as the grain size of Al-Mg alloy laser welds decreased, when Mg content was in the range higher than 1.9 wt.%.

• Journal of Korea Foundry Society
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• v.33 no.6
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• pp.233-241
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• 2013

Effect of Fe and Mn contents on the castability of Al-9wt%Si-xMg-yFe-zMn alloy has been studied. The alloy was composed of ${\alpha}$-Al phase, Al+eutectic Si phase, ${\beta}$-Al5FeSi compound and chinese script ${\alpha}$-$Al_{15}(Mn,Fe)_3Si_2$ compound. ${\beta}$-$Al_5FeSi$ and ${\alpha}$-$Al_{15}(Mn,Fe)_3Si_2$ compounds assumed to effect the fluidity and shrinkage behaviors of the alloy during solidification due to the crystallization of ${\alpha}$-$Al_{15}(Fe,Mn)_3Si_2$ and ${\beta}$-$Al_5FeSi$ compounds above eutectic temperature. As Fe and Mn contents of Al-9wt%Si-0.3wt%Mg system alloy increased from 0.15wt% to 0.6wt% and from 0.3wt% to 0.7wt%, fluidity of the alloy decreased by 5.7% and 3.3%, respectively. And as Mg content of Al-9wt%Si-0.45wt%Fe-0.5wt%Mn system alloy increased from 0.3wt% to 0.4wt%, fluidity of the alloy decreased by 8.6%. When Fe content of the alloy increased from 0.15wt% to 0.6wt%, macro shrinkage ratio decreased from 6.1% to 4.1%, and micro shrinkage ratio increased from 0.04% to 0.24%. Similarly, Mn content of the alloy increased from 0.3wt% to 0.7wt%, macro shrinkage ratio decreased from 6.0% to 4.5% and micro shrinkage ratio increased from 0.12% to 0.18%. Judging from the castability of the alloy, Al-9wt%Si-0.3wt%Mg alloy with low content of Fe and Mn, 0.1wt% Fe and 0.3wt% Mn, is recommendable.

• Journal of Korea Foundry Society
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• v.29 no.5
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• pp.213-219
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• 2009

Optimum conditions for production of semi-solid Al-Zn-Mg alloy billets was carried out by the Taguchi design method. And, Al-Zn-Mg alloy billets contained Sc (free, 0.1 and 0.3 mass %) were fabricated at optimum conditions. Evolution of microstructure in semi-solid state was investigated through various liquid fractions, holding times and holding temperatures. The Al-Zn-Mg alloy billets reheated at $615^{\circ}C$ during 30min are grain growth and it was fractured due to increasing liquid fraction before quenching. And, during reheating up to $600^{\circ}C$, grain growth of Al-Zn-Mg alloy billets contained Sc (0.1 and 0.3 mass %) was not occurred in comparison with those of Al-Zn-Mg alloy without Sc. It was thought that $Al_3Sc$ phases have a pinning effect in grain boundary and Sc content of 0.1 mass% is able to inhibit grain growth effectively through reheating process.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.1
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• pp.23-28
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• 2004

In this work, the effect of Sc and Mm(misch metal) on the high temperature behavior of Al-Mg alloys was observed. Hardness was increased due to appearance of fine $Al_3Sc$ precipitates. The elongation of Al-Mg-Sc alloy at high temperature was higher than that of Al-Mg-Sc-Mm alloy because Al-Mg-Sc alloy has finer grain sizes than Al-Mg-Sc-Mm alloy. The strain rate sensitivity factor, "m" of Al-Mg-Sc and Al-Mg-Sc-Mm at $475^{\circ}C$ and $1{\times}10^{-2}s^{-1}$ were 0.33 and 0.46, respectively. The activation energy of Al-Mg-Sc and Al-Mg-Sc-Mm alloy for superplastic deformation was 133KJ/mol and 103KJ/mol respectively. The elongation of Al-Mg-Sc alloy at high temperature was decreased by the addition of Mm, but the strength at high temperatures and low strain rate was improved.

• Journal of the Korean Ceramic Society
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• v.33 no.9
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• pp.985-994
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• 1996

The initiation and growth of $\alpha$-Al2O3/metal composites by the directed oxidation of molten commercial AlZnMg-alloy at 1223-1423K were investigated. Spontaneous bulk growth did not occur on the alloy alone. but the uniform initiation and growth of the composite were obtained by putting a thin layer of SiO2 particles on the surface of the alloy. Without SiO2 the external surface of the oxide layer was convered by MgO and MgAl2O4. But with the SiO2 reaction initiate the porous ZnO layers were found on the growth surface. The higher process temperature yielded a lower metal content. The oxidation product of $\alpha$-Al2O3 was found to be oriented with c-axis parallel to th growth direction. The growth rates increased with temperature and the apparent activation energy was 111.8 kJ/mol.

• Journal of Surface Science and Engineering
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• v.39 no.1
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• pp.25-34
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• 2006

Al-Mg alloy, an open rack vaporizer(ORV) material was reported to be corroded in seawater environments though the ORV material was coupled to thermally sprayed Al-Zn alloy functioning a sacrificial anode. In addition, the corrosion behavior based on the calculated corrosion potential did not match the observed corrosion behavior. Hence, the goal of this study is to get better understanding on Al or Al-Mg alloy coupled to Al-Zn alloy and to provide the calculated corrosion potential representing the corrosion behavior of the ORV material by immersion test, electrochemical tests, and calculation of corrosion and galvanic potential. The corrosion potentials of Al and Al alloys also depended on alloying element as well as surface defects. The corrosion potentials of Al and Al-Mg alloy were changed with time. In the meantime, the corrosion potentials of Al-Zn alloys were not. The corrosion rates of Al-Zn alloys were exponentially increased with zinc contents. The phenomena were explained with the stability of passive film proved by passive current density depending on pH and confirmed by the model proposed by McCafferty. Dissimilar material crevice corrosion (DMCC) test shows that higher content of zinc caused Al-Mg alloy corroded more rapidly, which was due to the fact that higher corrosion rate of Al-Zn makes [$H^+$] and [$Cl^-$] more concentrated within pit solution to corrode Al-Mg alloy. Considering electrochemical reactions within pit as well as bulk in the calculation gives better prediction on the corrosion behavior of Al and Al-Mg alloy as well as the capability of Al-Zn alloy for corrosion protection.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.287-293
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• 2021

This study was intended to investigate the influence of Al content on hardness and microstructural characteristics of discontinuous precipitates (DPs) formed by isothermal aging in Mg-8.7%Al and Mg-10%Al alloys. In order to obtain large amount of DPs in the microstructure, the alloy specimens were solution-treated at 688K for 24 h followed by water quenching, and then aged at 418K for 48h. The Mg-Al alloy with higher Al content was characterized by higher volume fraction of DPs at the same aging condition, lower interlamellar spacing of the DPs, thinner β phase layer and higher β phase content in the DPs. This is closely related to the higher velocity of discontinuous precipitation process resulting from the higher Al supersaturation in the α-(Mg) matrix. The Mg-10%Al alloy showed higher hardness of the DPs and greater difference in hardness between as-cast state and DPs than the Mg-8.7%Al alloy.

• Journal of Korea Foundry Society
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• v.21 no.2
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• pp.127-134
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• 2001

Misch metal (rare earth element, Ce, La, Nd, Pr) which has large influence on high-temperature stability and toughness was added to the Al-5%Ni-5%Mg alloy, and squeeze casting was used for Al-5%Ni-5%Mg-(Mm) alloys. The effect of applied pressure and misch metal additions on mechanical properties in Al-5%Ni-5%Mg alloy by direct squeeze casting has been investigated. The applied pressure were 0 MPa(gravity casting), 25, 50 and 75 MPa. Squeeze-cast Al-5%Ni-5%Mg-(Mm) alloys had better mechanical properties than those of non-pressurized cast alloys because of the increased cooling rate by the application of pressure during solidification. By the addition of misch metal in Al-5%Ni-5%Mg alloy, better combination of strength and elongation was obtained. The addition of 0.3%Mm in Al-5%Ni-5%Mg alloy improved the heat resistant property due to the formation of fine eutectic phases.

• Corrosion Science and Technology
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• v.23 no.2
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• pp.113-120
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• 2024

An attempt was made to apply digital image correlation (DIC) strain analysis to in-situ scanning electron microscopy (SEM) observations of bending deformation to quantify local strain distribution inside a ZnMgAl-alloy coating in deformation. Interstitial-free steel sheets were hot-dipped in a Zn-3Mg-6Al (mass%) alloy melt at 400 ℃ for 2 s. The specimens were deformed using a miniature-sized 4-point bending test machine inside the SEM chamber. The observed in situ SEM images were used for DIC strain analysis. The hot-dip ZnMgAl-alloy coating exhibited a solidification microstructure composed of a three-phase eutectic of fine Al (fcc), Zn (hcp), and Zn2Mg phases surrounding the primary solidified Al phases. The relatively coarsened Zn₂Mg phases were locally observed inside the ZnMgAl-alloy coating. The DIC strain analysis revealed that the strain was localized in the primary solidified Al phases and fine eutectic microstructure around the Zn₂Mg phase. The results indicated high deformability of the multi-phase microstructure of the ZnMgAl-alloy coating.