• 한국주조공학회지
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• 제33권2호
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• pp.55-62
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• 2013

Effect of Fe and Mn contents on the castability of Al-4wt%Mg-0.9wt%Si system alloy has been studied. According to the analysis of cooling curve for Al-4wt%Mg-0.9wt%Si-0.3wt%Fe-0.3/0.5wt%Mn alloy, ${\alpha}-Al_{15}(Fe,Mn)_3Si_2$ and ${\beta}-Al_5FeSi$ phases crystallized above eutectic temperature of $Mg_2Si$. Therefore, these phases affected both the fluidity and shrinkage behaviors of the alloy during solidification. As Fe and Mn contents of Al-4wt%Mg-0.9wt%Si system alloy increased from 0.1 wt% to 0.4 wt% and from 0.3 wt% to 0.5 wt% respectively, the fluidity of the alloy decreased by 26% and 33%. When Fe content of the alloy increased from 0.1 wt% to 0.4 wt%, 23% decrease of macro shrinkage and 19% increase of micro shrinkage appeared. Similarly, Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, 11% decrease of macro shrinkage and 14% increase of micro shrinkage appeared. Judging from the castability of the alloy, Al-4wt%Mg-0.9wt%Si alloy with low content of Fe and Mn, 0.1 wt% Fe and 0.3 wt% Mn, is recommendable.

• 한국주조공학회지
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• 제31권1호
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• pp.18-25
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• 2011

Effect of Fe and Mn contents on the tensile properties has been studied in Al-9wt%Si-0.3wt%Mg alloy. As Fe content of Al-9wt%Si-0.3wt%Mg-0.5wt%Mn alloy increased from 0.15wt% to 0.45wt%, tensile strength of as-cast alloy decreased from 192 MPa to 174 MPa, and elongation of the alloy also decreased from 4.8% to 4.2%. Decrease of these properties can be explained as the formation of plate shape, ${\beta}-Al_5FeSi$ phase with high Fe/Mn ratio of the alloy. However when Mn content of Al-9wt%Si-0.3wt%Mg-0.45wt%Fe alloy increased from 0.3wt% to 0.5wt%, tensile strength of T6 aged alloy increased from 265 MPa to 275 MPa, and elongation of the alloy increased from 2.3% to 3.6%. These improvements attribute to chinese script, ${\alpha}-Al_{15}(Mn,Fe)_3Si_2$ phase shape-modified from ${\beta}-Al_5FeSi$ phase with low Fe/Mn ratio of the alloy.

• 동력기계공학회지
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• 제21권2호
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• pp.14-19
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• 2017

The corrosion characteristics of Al-Si-Mg alloy were investigated in $O_2$ and $H_2S/H_2$ environments at high temperature. The weight gain and the reaction rate constant of the Al-Si-Mg alloy were measured in the oxygen and hydrogen sulfide environments at 773K. The weight gain of Al-Si-Mg alloy was showed parabolic increase in the oxygen and hydrogen sulfide environments. The reaction rate constants were confirmed to be $1.45{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the oxygen environment and $6.19{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the hydrogen sulfide environment respectively. As a result of XPS analysis on the specimen surface, $Al_2O_3$ and MgO compounds were detected in oxygen environment and $Al_2(SO_4)_3$ sulfate was detected in the hydrogen sulfide environment. Corrosion rate of Al-Si-Mg alloy was about 4.3 times faster in hydrogen sulfide environment than oxygen environment.

• 한국세라믹학회지
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• 제33권9호
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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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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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.

• 한국주조공학회지
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• 제26권6호
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• pp.249-257
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• 2006

The effects of alloying element and the condition of heat-treatment on the strength of squeeze-cast Al-3.0 wt%Si alloy were investigated. The strength of the alloy without grain refinement was increased with increase Cu content upto 3.0 wt% and rather decreased beyond that. The tensile strength of the alloy with grain refinement increased with Cu content upto 3.0 wt% and not changed beyond that. The strength of the alloy without grain refinement increased with the Mg content. The tensile strength with grain refinement increased with the Mg content upto 0.50 wt% and then decreased beyond that. The strength of the grain refined alloy increased by individual and simultaneous additions of Cu and Mg and the maximum strength was obtained with Al-3.0 wt%Si-4.5 wt%Cu-0.50 wt%Mg alloy. The optimum heat-treatment condition for this alloy was obtained.

• 한국주조공학회지
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• 제33권3호
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• pp.103-112
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• 2013

Effect of Fe and Mn contents on the tensile properties of Al-4 wt%Mg-0.9 wt%Si alloy system has been studied. Common phases of Al-4 wt%Mg-0.9 wt%Si alloy system were ${\alpha}$-Al, $Mg_2Si$, ${\alpha}-Al_{12}(Fe,Mn)_3Si$ and ${\beta}-Al_5FeSi$. As Fe content of Al-4 wt%Mg-0.9 wt%Si alloy system increased from 0.15 wt% to above 0.3 wt%, ${\beta}-Al_5FeSi$ compound appeared. When Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, morphology of plate shaped ${\beta}-Al_5FeSi$ compound changed to chinese script ${\alpha}-Al_{12}(Fe,Mn)_3Si$. As Fe content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Mn alloy increased from 0.15 wt% to 0.4 wt%, tensile strength of the as-cast alloy decreased from 191 MPa to 183 MPa and, elongation of the alloy also decreased from 8.0% to 6.2%. Decrease of these properties can be explained as the formation of plate shape, ${\beta}-Al_5FeSi$ phase with low Mn/Fe ratio of the alloy. However, when Mn content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Fe alloy increased from 0.3 wt% to 0.5 wt%, tensile strength of as-cast alloy increased from 181 MPa to 194 MPa and, elongation of the alloy increased from 6.8% to 7.0%. These improvements attribute to the morphology change from ${\beta}-Al_5FeSi$ phase to chinese script, ${\alpha}-Al_{15}(Fe,Mn)_3Si_2$ phase shape-modified from with high Mn/Fe ratio of the alloy.

• 한국주조공학회지
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• 제32권6호
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• pp.289-295
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• 2012

Mg-Al-Sn-Si system alloy, as a promising cheap heat-resistant Mg alloy for automobile engine part, has been investigated. Refinement of microstructure and precipitation of thermally stable secondary phases are important goal for the design of heat-resistant Mg alloy. In this study, the effect of Ce on the microstructure and room temperature mechanical properties of Mg-Al-Sn-Si alloy was investigated. High thermally stable $Mg_2Si$ phases in Mg-Al-Sn-Si alloy is very useful intermetallic compound. However, the $Mg_2Si$ phases often result in poor mechanical properties due to the coarse chinese type $Mg_2Si$ phases. The experimental specimens were fabricated by fluxless melting under $CO_2+SF_6$ atmosphere and poured into the permanent pre-heated at $200^{\circ}C$. It was told that Ce addition can modify $Mg_2Si$ phases and refine microstructure and improve the tensile strength, yield strength and elongation.

• 한국분말재료학회지
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• 제21권6호
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• pp.460-466
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• 2014

Al-Si-SiC composite powders with intra-granular SiC particles were prepared by a gas atomization process. The composite powders were mixed with Al-Zn-Mg alloy powders as a function of weight percent. Those mixture powders were compacted with the pressure of 700 MPa and then sintered at the temperature of $565-585^{\circ}C$. T6 heat treatment was conducted to increase their mechanical properties by solid-solution precipitates. Each relative density according to the optimized sintering temperature of those powders were determined as 96% at $580^{\circ}C$ for Al-Zn-Mg powders (composition A), 97.9% at $575^{\circ}C$ for Al-Zn-Mg powders with 5 wt.% of Al-Si-SiC powders (composition B), and 98.2% at $570^{\circ}C$ for Al-Zn-Mg powders with 10 wt.% of Al-Si-SiC powders (composition C), respectively. Each hardness, tensile strength, and wear resistance test of those sintered samples was conducted. As the content of Al-Si-SiC powders increased, both hardness and tensile strength were decreased. However, wear resistance was increased by the increase of Al-Si-SiC powders. From these results, it was confirmed that Al-Si-SiC/Al-Zn-Mg composite could be highly densified by the sintering process, and thus the composite could have high wear resistance and tensile strength when the content of Al-Si-SiC composite powders were optimized.

• 한국분말재료학회지
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• 제26권2호
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• pp.138-145
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• 2019

In this study, Al-Si-Mg alloys are additively manufactured using a selective laser melting (SLM) process from AlSi10Mg powders prepared from a gas-atomization process. The processing parameters such as laser scan speed and laser power are investigated for 3D printing of Al-Si-Mg alloys. The laser scan speeds vary from 100 to 2000 mm/s at the laser power of 180 and 270 W, respectively, to achieve optimized densification of the Al-Si-Mg alloy. It is observed that the relative density of the Al-Si-Mg alloy reaches a peak value of 99% at 1600 mm/s for 180 W and at 2000 mm/s for 270W. The surface morphologies of the both Al-Si-Mg alloy samples at these conditions show significantly reduced porosities compared to those of other samples. The increase in hardness of as-built Al-Si-Mg alloy with increasing scan speed and laser power is analyzed due to high relative density. Furthermore, it was found that cooling conditions after the heat-treatment for homogenization results in the change of dispersion status of Si phases in the Al-Si matrix but also affects tensile behaviors of Al-Si-Mg alloys. These results indicate that combination between SLM processing parameters and post-heat treatment should be considered a key factor to achieve optimized Al-Si alloy performance.