• 한국분말재료학회지
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• 제10권1호
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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$.

• 한국분말재료학회지
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• 제9권2호
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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.

• 한국분말재료학회지
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• 제12권2호
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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.

• 대한금속재료학회지
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• 제50권7호
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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.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1037-1038
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• 2006

The increasing demand of PM parts for automobile and aerospace applications has caused a strong development of the aluminium based metal matrix composites (MMCs).Aluminium alloys are one of most widely used materials as matrix in MMCs, both in research and development as well as in industrial applications. In the present work, the influence of the ceramic reinforcement addition to a 2xxx series aluminium alloy is studied. Several percentages of TiCN have been added to the Al-Cu alloy using PM techniques, in order to analyze its influence on the liquid phase sintering process and on the final properties of the material.

• 한국표면공학회지
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• 제41권3호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.234-237
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• 2004

As an automotive industry's demand for lighter materials gets bigger and bigger, a lot of new strength Al alloys have been developed recently. In the present study, Al 6xxx series alloys were designed to get the strength level of 350MPa with the elongation of $12\%$. For that purpose, three alloy systems were selected based on the thermodynamics calculation. The effect of both $Mg_{2}Si$ precipitate and excess Si amount on the newly designed alloys was investigated. Also, heat treatment procedure was studied to optimize the mechanical properties.

• 열처리공학회지
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• 제11권3호
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• pp.200-206
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• 1998

The aim of this study is to investigate the effect of impurity level and fabrication processes on the strength, impact and fracture toughness of 7075, 7050 and 7175 aluminum alloy forgings. A specially processed 7175S-T74 aluminum forgings was superior to a conventionally processed 7075-T73, 7050-T74 and 7175-T74 aluminum forgings in both strength and toughness. The reduction of impurity level of iron and silicon has significantly diminished the size and volume fraction of second phase particles such as $Al_7Cu_2Fe$ and $Mg_2Si$. A further reduction of the amount of second phase particles has been observed by applying a special fabrication process. This phenomena result from the application of intermediate soaking at higher temperature and more sufficiant hot working temperature than that of a conventional processing.

• 소성∙가공
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• 제30권3호
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• pp.142-148
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• 2021

In hot forging analysis, the interfacial heat transfer coefficient (IHTC) is a very important factor defining the heat flow between the die and the material. In particular, in the hot forging analysis of aluminum 6xxx series alloy, which are used in automobile parts, differences in load and microstructure occur due to changes in surface temperature according to the IHTC. This IHTC is not a constant value but changes depends on pressure. This study derived the IHTC under low load using aluminum 6082 alloy. An experiment was performed by fabricating a compression die, and a heat transfer analysis was performed based on the experimental data. The heat transfer analysis used DEFORM-2D, a commercial finite element analysis program. To derive the IHTC, heat transfer analysis was performed for the IHTC in the range of 10 to 50 kW/m²℃ at intervals of 10kW/m²℃. The heat transfer analysis results according to the IHTC and the actual experimental values were compared to derive the IHTC of the aluminum 6082 alloy under low load.

• 열처리공학회지
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• 제9권3호
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• pp.161-168
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• 1996

The purpose of this study is to investigate the effect of impurity level and fabrication processes on the strength, fracture toughness and fatigue resistance of 7075, 7050 and 7175 high strength aluminum forgings. It has been verified that plane strain fracture toughness and fatigue characteristics of a specially processed 7175S-T74 alloy is superior to a conventionally processed 7075-T6/T73, 7050-T74 and 7175-T74 alloys. These beneficial effects primarily arise from two view points, i.e., the effect of reducing the impurity level of iron and silicon has significantly diminished the size and volume fraction of second phase particles such as $Al_7Cu_2Fe$ and $Mg_2Si$. Futher reduction of the amount of nonequilibrium second phase particles has been observed by applying a special fabrication process.