• Journal of Powder Materials
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• v.10 no.1
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• pp.40-45
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• 2003

Sintering behavior of 2xxx series Al alloy was investigated to obtain full densification and sound microstructure. The commercial 2xxx series Al alloy powder. AMB2712, was used as a starting powder. The mixing powder was characterized by using particle size analyzer, SEM and XRD. The optimum compacting pressure was 200 MPa, which was the starting point of the "homogeneous deformation" stage. The powder compacts were sintered at $550~630^{\circ}C$ after burn-off process at $400^{\circ}C$. Swelling phenomenon caused by transient liquid phase sintering was observed below $590^{\circ}C$ of sintering temperature. At $610^{\circ}C$, sintering density was increased by effect of remained liquid phase. Further densification was not observed above $610^{\circ}C$. Therefore, it was determined that the optimum sintering temperature of AMB2712 powder was $610^{\circ}C$.}C$.

• Journal of Powder Materials
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• v.9 no.2
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• pp.116-123
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• 2002

The characteristics of two commercial 2xxx series Al alloy powders, AMB2712 and 201AB, were evaluated and their compacting and sintering characteristics were discussed in tems of compacting pressure. The particle shapes of both two powder mixtures were irregular and their particle size distributions were broad. The compactibility of AMB2712 was superior to that of 201AB because of better fluidity. The sintered density was higher than the green density at low compacting pressure, however, it was lower than the green density when the samples were compacted at higher pressure due to the selling during sintering. The sintered density was alomost the same as the green density at the "homogeneous deformation" stage. It was observed that pores were created at the triple points due to the rapid diffusion of Cu in Al. Cu in Al.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.9-10
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• 2002

• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.131-135
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• 2005

7xxx series Al alloy has the most attractive properties including its excellent high specific strength, stress corrosion cracking and corrosion-resistance. However, in case of the Al-Zn system, the liquid phase has a transient aspect because of the high solid solubility of Zn in Al. Therefore, transient liquid phase sintering behavior was observed during the sintering process. And the amount of liquid and its duration were influenced by the process variables including heating rate and final sintering temperature. At high heating rates($100^{\circ}C/min$), the liquid fraction increased during sintering because diffusion was minimized and therefore local saturation could easily occur. The sintered density increased with increasing heating rate.

• Journal of Powder Materials
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• v.13 no.3 s.56
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• pp.172-177
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• 2006

Aging characteristics and mechanical properties of commercial 7xxx series Al composites were investigated from viewpoint of ceramic contents. After sintering process, sintered densities of blended and composite powder were 95 and 97%, respectively. Each part was solution-treated at $475^{\circ}C$ for 60 min and aged $175^{\circ}C$. And two-step aging was also performed form $120^{\circ}C$ to $175^{\circ}C$. The aging behavior of the sintered composite pow-der was different from that of sintered blended powder. The peak aging time of the composite was rapid as well due to strain. Before aging, mechanical properties of sintered composite powder was significantly higher than that of sintered blended powder. These increments of properties were directly affected by ceramic particles. However, after aging, incremental rate of mechanical properties was slowed in the composite.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1063-1064
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• 2006

Mechanical properties of 7xxx series Al metal matrix composite (MMC) powders containing different amounts of ceramic were investigated. The ceramic contents of the starting powders were 5 wt.% or 10 wt.%. The powders were uniaxially cold compacted using a cylindrical die with a compacting pressure of 250 MPa and were sintered at $620^{\circ}C$ in a dry $N_2$ atmosphere for 60 min. For the heat treatment, sintered parts were solution treated at $475^{\circ}C$ and aged at $175^{\circ}C$. Compression tests were conducted to reveal the effect of $Al_2O_3$ particle content on the mechanical properties of the composites. Fractography was examined using a scanning electron microscope.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1065-1066
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• 2006

The aging behavior of sintered Al composites with various ceramic contents was investigated. 2xxx series blended powder was used as the starting powder. Ceramic contents were 0wt.% and 5wt.%. The blended powders were compacted at 250MPa. The sintering process was performed at $620^{\circ}C$ for 60min in a $N_2$ atmosphere. Each part was solution-treated at $518^{\circ}C$ for 60min and aged at $180^{\circ}C$. The Rockwell hardness at the peak aging time increased with ceramic contents. However, the peak aging time at maximum hardness was reduced with increased ceramic contents.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.11a
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• pp.24-24
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• 2004

• Korean Journal of Metals and Materials
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• v.50 no.7
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• pp.503-509
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• 2012

We report on the feasibility of producing 6xxx series Al alloy sheets using a combination of twin-roll strip casting and asymmetric rolling. The Al alloy sheets produced in this study exhibited an excellent formability ($\bar{r}=1.2$, ${\Delta}r=0.17$) and mechanical properties (${\sigma}_{TS}{\sim}260MPa$, ${\varepsilon}>30%$), which cannot be feasibly obtained via the conventional technique based on ingot casting and conventional rolling. The enhanced formability as evaluated in terms of $\bar{r}$ and ${\Delta}r$ was clarified by examining the evolution of textures associated with strip casting and subsequent thermo-mechanical treatments. The evaluation of the formability leads us to conclude that the combined technique based on strip casting and asymmetric rolling is a feasible process for enhancing the formability of Al alloy sheets to a level beyond which the conventional technique can reach.

• Journal of the Korean institute of surface engineering
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• v.41 no.3
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• pp.109-113
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• 2008

High strength 7xxx series Al-Zn-Mg alloy have been investigated for using light weight automotive parts especially for bump back beam. The composition of commercial 7xxx aluminum has the Zn/Mg ratio about 3 and Cu over 2 wt%, but this composition isn't adequate for appling to automotive bump back beam due to its high resistance to extrusion and bad weldability. In this study the Zn/Mg ratio was increased for better extrusion and Cu content was reduced for better welding. With this new composition we investigated the effect of composition on the resistivity against stress corrosion cracking. As the Zn/Mg ratio is increased fracture energy obtained by slow strain rate test was decreased, which means degradation of SCC resistance. While the fracture energy was increased with Cu contents although it is below 1%, which means improvement of SCC resistance. These effects of composition change on the SCC resistivity were identified by observing the fracture surface and crack propagation.