• Journal of the Korean institute of surface engineering
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• v.32 no.2
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• pp.100-108
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• 1999

The microstructure and corrosion properties of Al-Si diffusion coated PWA1426 alloy have been investigated. Experimental variables are included temperatures of heat-treatment and coating thickness. The microstructure of coated layer and corrosion properties were analysed by SEM, EDS and hot corrosion test. Two major processes have been found to contribute to microstructural changes in the coating. These are, firstly, the transformation of the NiAl to other $Ni_2Al_3$-based phase and secondly, the precipitation of Cr containing phases. Specimens heat treated at $1080^{\circ}C$ showed superior corrosion resistance to heat treated at $880^{\circ}C$. These increase in life was attributed to the transformation of NiAl and increased coating thickness of PWA1426 alloy.

• Journal of Korea Foundry Society
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• v.30 no.1
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• pp.34-45
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• 2010

The effects of alloy elements and cooling rate on the solidification path and the formation behavior of $\beta$ phase in Fe-containing Al-Si alloys were studied based on the thermodynamic analysis and the pertinent experiments. The thermodynamic calculation was systematically performed by using Thermo-Calc program. For the thermodynamic analysis in high alloy region of Al-Si-Fe ternary system, a thermodynamic database for Thermo-Calc was correctly updated and revised by the collected up-to-date references. For the thermodynamic-based prediction of various solidification paths in Fe-containing Al-Si system, liquidus projection of Al-Si-Fe ternary system, including isotherms, invariant, monovariant, bivariant reactions and equilibrium temperatures, was calculated and analyzed as functions of composition and temperature. The calculated results were compared to the experimental results using various casting specimens. In order to analyze various solidification sequences as functions of Si and Fe content, 4 representative alloy compositions, low Fe content in both low and high Si contents and high Fe content again in both low and high Si contents, were designed in this study. For better understanding of the influence of cooling rate on the formation behavior of $\beta$ phase, 4 alloys were solidified under furnace and rapidly cooled conditions. Cooling curves of solidified alloys were recorded by thermal analysis. Various important solidification events were evaluated using the first derivative-cooling curves. Microstructures of the casting samples were studied by the combined analysis of optical microscopy (OM) and scanning electron microscopy (SEM).

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.148-157
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• 1999

The objective of this study is to investigate the effect of three main chemical compositions(Mg, Zn, Si) on extrudability of 7xxx Al alloy with high tensile strength. A few Al alloys based on 7xxx alloys were metal mold cast with various weight*%) of Mg 0.3-1.2%, Zn 5.0-8.0% and Si 0.4-0.7%, to envestigate the effects of extrudability, as well as mechanical properties. To measure the extrudability of cast billets, maximum extrusion pressure and surface temperature at die exit before tearing occurs were obtained by experiment and simulation of thermo-viscoplastic F.E.M. Also the yield and tensile strength of extruded products were tested.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.53-53
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• 2010

Car industry has required light-weight steels, but still with strong mechanical strength. To meet this requirement, a variety of researches on Fe-Al alloys have been performed. As Al is being added in a disordered manner, alloys become more ductile and show higher yield stress. At a certain concentration of Al, however, the Fe-Al alloy system falls in a second phase whose mechanical strength is worsened. To understand the microscopic role of Al, we investigate the stability and the elastic properties of various Fe-Al alloys using ab initio density functional theory. At agiven Al concentration, the equilibrium geometry is obtained among several disordered Fe-Al alloy structures by performing the geometry relaxation. The formation energies and elastic properties such as bulk moduli of the equilibrium structures are also computed as a function of Al concentration. We also investigate the effects of different elements such as Si and Mn. Fe-Si alloy systems exhibit unusual mechanical behaviors requiring further investigation to understand their physical origin. Especially, the microscopic role of Mn is investigated to find its physical origin of preventing the Fe-Al alloy system from forming an unfavorable second phase. The effect of manganese on mechanical properties of Fe-based alloys is also explored.

• Korean Journal of Materials Research
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• v.33 no.1
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• pp.8-14
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• 2023

In order to broaden the range of application of light weight aluminum alloys, it is necessary to enhance the mechanical properties of the alloys and combine them with other materials, such as cast iron. In this study, the effects of adding small amounts of Cu and Zr to the Al-Si-Mg based alloy on tensile properties and corrosion characteristics were investigated, and the effect of the addition on the interfacial compounds layer with the cast iron was also analyzed. Although the tensile strength of the Al-Si-Mg alloy was not significantly affected by the additions of Cu and Zr, the corrosion resistance in 3.5 %NaCl solution was found to be somewhat lowered in this research. The influence of Cu and Zr addition on the type and thickness of the interfacial compounds layer formed during compound casting with cast iron was not significant, and the main interfacial compounds were identified to be Al₅FeSi and Al₈Fe₂Si phases, as in the case of the Al-Si-Mg alloys.

• 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.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.11a
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• pp.40-41
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• 2000

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.227-232
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• 2013

Al-based alloys have recently attracted considerable interest as structural materials and light weight materials due to their excellent physical and mechanical properties. For the investigation of the potential of Al-based alloys, a surface porous $Al_{88}Cu_6Si_6$ eutectic alloy has been fabricated through a chemical leaching process. The formation and microstructure of the surface porous $Al_{88}Cu_6Si_6$ eutectic alloy have been investigated using X-ray diffraction and scanning electron microscopy. The $Al_{88}Cu_6Si_6$ eutectic alloy is composed of an ${\alpha}$-Al dendrite phase and a single eutectic phase of $Al_2Cu$ and ${\alpha}$-Al. We intended to remove only the ${\alpha}$-Al phase and then the $Al_2Cu$ phase would form a porous structure on the surface with open pores. Both acidic and alkaline aqueous chemical solutions were used with various concentrations to modify the influence on the microstructure and the overall chemical reaction was carried out for 24 hr. A homogeneous open porous structure on the surface was revealed via selective chemical leaching with a $H_2SO_4$ solution. Only the ${\alpha}$-Al phase was successfully leached while the morphology of the $Al_2Cu$ phase was maintained. The pore size was in a range of $1{\sim}5{\mu}m$ and the dealloying depth was nearly $3{\mu}m$. However, under an alkaline NaOH, aqueous solution, an inhomogeneous porous structure on the surface was formed with a 5 wt% NaOH solution and the morphology of the $Al_2Cu$ phase was not preserved. In addition, the sample that was leached by using a 7 wt% NaOH solution crumbled. Al extracted from the Al2Cu phase as ${\alpha}$-Al phase was dealloyed, and increasing concentration of NaOH strongly influenced the morphology of the $Al_2Cu$ phase and sample statement.

• Journal of Magnetics
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• v.16 no.4
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• pp.440-443
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• 2011

In this study, we investigated the glass-forming ability (GFA) and magnetocaloric effect (MCE) of $Gd_{55}Co_{20}Al_{23}Si_2$ bulk glassy alloy. It is found that the addition of 2 at% Si is effective for extension of the supercooled liquid region (${\Delta}T_x$), the ${\Delta}T_x$ is 55 K for the $Gd_{55}Co_{20}Al_{25}$ glassy alloy, and increases to 79 K for the $Gd_{55}Co_{20}Al_{23}Si_2$ alloy. As a result, $Gd_{55}Co_{20}Al_{23}Si_2$ glassy alloys with diameters up to 5 mm were successfully synthesized. The alloys also exhibit large MCE, i.e., the magnetic entropy change (${\Delta}S_m$) of 8.9 J $kg^{-1}\;K^{-1}$, the full width at half maximum of the ${\Delta}S_m$ (${\delta}T_{FWHM}$) of 87 K, and the refrigerant capacity (RC) of 774 J $kg^{-1}$.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.120-126
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• 2010

It was known that the excellent wear resistance of hyper eutectic aluminum alloy is based on the primary Si particles which are distributed in the base metal. When the primary Si volume fraction increases, the smaller size have excellent wear resistance characteristics. However, this trend always does not match. There is no investigation result based on the materials and methods for real using parts. In this study, using the automotive parts manufacturer currently in use hyper eutectic Al alloy tensile test specimen type sample was fabricated by 350Ton high pressure die-casting machine. Then, fluidity, tensile, impact and wear resistance properties were evaluated. If the casting quality, primary Si size, fraction and distribution are similar, mechanical properties and wear resistance are equivalent.