• Transactions of Materials Processing
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• v.21 no.7
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• pp.447-452
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• 2012

This paper is concerned with forming of Al-Zn-Mg-Sc aluminum alloy bolts, focusing on the effects of heat treatment and age-hardening on the formability and ductile damage evolution. Both experimental and finite element studies were performed. From the experiments, it is observed that the heat treatment or the normalization of Al-Zn-Mg-Sc aluminum alloy increases its formability dramatically resulting in successful bolt forming, while the effects of age-hardening at room temperature on the stress-strain relationship and formability are not very critical. Deformation characteristics such as distribution of effective stress and strain, material flow, and ductile damage evolution during bolt forming are examined using a commercial finite element package, Deform-2D. It should be noted that the extrusion load predicted by the finite element method matches well the experiment results. The finite element predictions on the deformation characteristics support the experimental observations such as fracture of bolt head flange, material flow, and distribution of hardness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.249-252
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• 1999

A numerical analysis was perfomed to predict flow curves and dynamic recrystallization behaviors of Al-5%Mg alloy on the basis of results of hot compression tests. The hot compression tests were carried out in the ranges of 350-50$0^{\circ}C$ and 5$\times${{{{ {10 }^{-3 } }}}}~3$\times${{{{ {10 }^{0 } }}}}/sec to obtain the Zener-Hollmon parameter. In the modelling equation the effects os strain hardening and dynamic recrystallization were taken into consideration. A model for predicting the evolution of microstructure in Al-5%Mg alloy during thermomechanical processing was developed in terms of dynamic recrystallization phenomena, The microstructure model was combined with finite element modeling(FEM) to predict microstructure development Model predictions showed good agreement with microstructures obtained in compression tests.

• Transactions of Materials Processing
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• v.8 no.6
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• pp.620-625
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• 1999

A finite element analysis is performed to predict the recrystallized volume fraction and the mean grain size in hot compression of Al-5wt%Mg alloy. In the analysis, a modeling equation of flow stress is assumed as a function of strain, strain rate, and temperature. And the influence of above varibles on flow stress is quantified by using Zener-Hollomon Parameter. In the modeling equation, effects of strain hardening and dynamic recrystallization on microstructure of Al-5wt%Mg alloy are investigated. The predicted results of recrystallized volume fraction and mean grain size are in good agreement with those of microstructures obtained from hot compression tests.

• Transactions of Materials Processing
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• v.26 no.5
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• pp.306-313
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• 2017

This study investigated the microstructure, tensile strength, and high cycle fatigue properties of ADC12 aluminum alloys with different $Mg+Al_2Ca$ contents manufactured using die casting process. Microstructural observation identified the presence of ${\alpha}-Al$, eutectic Si, $Al_2Cu$, and Fe-intermetallic phases. The increase of $Mg+Al_2Ca$ content resulted in finer pore size and decreased pore distribution. Room temperature tensile strength tests were conducted at strain rate of $1{\times}10^{-3}/sec$. For 0.6%Mg ADC12, measured UTS, YS, and El were 305.2MPa, 157.0MPa, and 2.7%, respectively. For 0.8%Mg ADC12, measured UTS, YS, and El were 311.2 MPa, 159.4 MPa, and 2.4%, respectively. Therefore, 0.8% ADC12 alloy had higher strength and slightly decreased elongation compared to 0.6% Mg ADC12. High cycle fatigue tests revealed that 0.6% Mg ADC12 alloy had a fatigue limit of 150 MPa while 0.8% Mg ADC12 had a fatigue limit of 160MPa. It was confirmed that $Mg+Al_2Ca$ added ADC12 alloy achieved finer, spherical eutectic Si particles, and $Al_2Cu$ phases with greater mechanical and fatigue properties since size and distribution of pores and shrinkage cavities decreased as $Mg+Al_2Ca$ content increased.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1000-1001
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• 2006

Two atomized alloy powders were pre-compacted by cold and subsequently hot forged at temperatures ranging from 653K to 845K. The addition of Cu and Mg causes a decrease in the eutectic reaction temperature of Al-10Si-5Fe-1Zr alloy from 841K to 786K and results in a decrease of flow stress at the given forging temperature. TEM observation revealed that in addition to Al-Fe based intermetallics, $Al_2Cu$ and $Al_2CuMg$ intermetallics appeared. The volume fraction of intermetallic dispersoids increased by the addition of Cu and Mg. Compressive strength of the present alloys was closely related to the volume fraction of intermetallic dispersoids.

• Transactions of Materials Processing
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• v.31 no.2
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• pp.73-80
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• 2022

In this study, a developed Mg-5Bi-2Al-0.4Mn (BAM520, wt%) alloy was successfully extruded at an extremely high speed of 70 m/min. Microstructural evolution during extrusion and the microstructural characteristics and tensile properties of the very-high-speed extruded BAM520 alloy were then investigated. The homogenized BAM520 billet contained only thermally stable Mg₃Bi₂ phase particles without any Mg₁₇Al₁₂ phase with a low melting temperature. Therefore, the BAM520 alloy exhibited excellent extrudability. The very-high-speed extruded BAM520 alloy had a completely recrystallized grain structure and a typical basal fiber texture. Despite the extremely high extrusion speed of 70 m/min, the extruded BAM520 alloy had a high ultimate tensile strength of 280 MPa due to combined strengthening effects of a small grain size, numerous fine Mg₃Bi₂ particles, and strong basal texture.

• Journal of Korea Foundry Society
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• v.31 no.3
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• pp.145-151
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• 2011

Metallic foam has been known as a functional material which can be used for absorption properties of energy and sound. The unique characteristics of Al foam of mechanical, acoustic, thermal properties depend on density, cell size distribution and cell size, and these characteristics expected to apply industry field. Al-Zn-Mg-Cu alloy foams was fabricated by following process; firstly melting the Al alloy, thickening process of addition of Ca granule to increased of viscosity, foaming process of addition of titanium hydride powder to make the pores, holding in the furnace to form of cooling down to the room temperature. Metal foams with various porosity level were manufactured by change the foaming temperature. Compressive strength of the Al alloy foams was 2 times higher at 88% porosity and 1.2 times higher at 92% porosity than pure Al foams. It's sound and vibration absorption coefficient were higher than pure Al foams and with increasing porosity.

• Journal of the Korean Society for Heat Treatment
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• v.10 no.2
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• pp.81-92
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• 1997

The effect of alloying elements, precipitate size, its distribution, and dislocation substructure resulted from warm rolling or cold rolling in the superplastic Al-Mg alloy system was investigated. One of the major requirements for fine structure superplasticity is that the grain size should be very small. Fine grain structure is controlled by the dislocation substructure and the dynamic recrystallization during hot or warm working. The recovery of Al-Mg base alloys was constrained resulting in relatively high dislocation density when the alloys were warm rolled. In particular, Al-Mg-Zr alloy exhibited the smallest sub-grain size among Al-Mg alloys containing Mn, Cu, Zr as a third element. The Al-Mg-Mn alloy cold rolled 80% after hot rolling showed the maximun strain rate sensitivity exponent, m, of 0.75 under strain rate of $7.1{\times}10^{-4}/s$ at $500^{\circ}C$. The elongation of the alloys was limited in spite of high m values due to large dispersoids containing appreciable amount of Fe impurities.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.483-490
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• 1997

Al2O3/metal composites were fabricated by oxidation and reaction of molten Al-alloy into two types of commercial Al2O3-SiO2 fibrous insulation board. The growth rate, composition and microstructure of these materials were described. An AlZnMg(7075) alloy was selected as a parent alloy. Mixed polycrystalline fiber and glass phase fiber were used as a filler. The growth surface of an alloy was covered with and without SiO2. SiO2 powder was employed as a surface dopant to aid initial oxidation of Al-alloy. Al-alloy, SiO2, fiber block and growth inhibitor CaSiO3 were packed sequentially in a alumina crucible and oxidized in air at temperature range 90$0^{\circ}C$ to 120$0^{\circ}C$. The growth rate of composite layer was calculated by measuring the mass increasement(g) per unit surface($\textrm{cm}^2$). XRD and optical microscope were used to investigate the composition and phase of composites. The composite grown at 120$0^{\circ}C$ and with SiO2 dopant showed rapid growth rate. The growth behavior differed a little depending on the types of fiber used. The composites consist of $\alpha$-Al2O3, Al, Si and pore. The composite grown at 100$0^{\circ}C$ exhibited better microstructure compared to that grown at 120$0^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.3
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• pp.144-148
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• 2011

Change in damping capacity with strain amplitude was studied in Mg-Al-Si alloy in as-cast, solution-treated and aged states, respectively. The as-cast microstructure of the alloy is characterized by eutectic ${\beta}$($Mg_{17}Al_{12}$) phase and Chinese script type $Mg_2Si$ particles. The solution treatment dissolved the ${\beta}$ phase into the matrix, while the aging treatment resulted in the distribution of continuous and discontinuous type ${\beta}$ precipitates. The solution-treated microstructure showed better damping capacity than as-cast and aged microstructures both in strain-dependent and strain-independent damping regions. The decrease in second-phase particles which weakens the strong pinning points on dislocations and distribution of solute atoms in the matrix, would be responsible for the enhanced damping capacity after solution treatment.