Journal of Powder Materials

Si-Young Chang

3 Articles

Aging Characteristics of 7xxx Series Al Composites with Al₂O₃: Kyung-Ho Min, Kwang-Hyun Park, Young-Ik Seo, Si-Young Chang, Young-Do Kim; J Korean Powder Metall Inst. 2006;13(3):172-177.; DOI: https://doi.org/10.4150/KPMI.2006.13.3.172

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Abstract PDF: 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°C for 60 min and aged 175°C. And two-step aging was also performed form 120°C to 175°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.

Sintering Behavior of 7xxx Series Al Blended Powder with Variation of Heating Rate: Shin Kang, Kyung Min, Hyun Park, Si-Young Chang, Young Kim; J Korean Powder Metall Inst. 2005;12(2):131-135.; DOI: https://doi.org/10.4150/KPMI.2005.12.2.131

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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°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.

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Mechanical properties of sintered 7xxx series AI/SiCp composites
Kyung Ho Min, Baek-Hee Lee, Si-Young Chang, Young Do Kim
Materials Letters.2007; 61(11-12): 2544. CrossRef

Preparation of Bi-materials by Powder Metallurgy Method: In-Gyu Lee, Kwang-Sik Lee, Si-Young Chang; J Korean Powder Metall Inst. 2004;11(6):462-466.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.462

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Abstract PDF: The bi-materials composed of Al-5wt%Mg and its composite reinforced with SiC particles were prepared by ball-milling and subsequent sintering process. The size of powder in Al-Mg/SiCp mixture decreased with increasing ball-milling time, it was saturated above 30 h when the ball and powder was in the ratio of 30 to 1. Both Al-5wt%Mg powders mixture and Al-5wt%Mg/SiCp mixture were compacted under a pressure of 350MPa and were bonded by sintering at temperatures ranging from 873K to 1173K for 1-5h. At 873k, the sound bi-mate-rials could not be obtained. In contrast, the bi-materials with the macroscopically well-bonded interface were obtained at higher temperatures than 873K. The length of well-bonded interface became longer with increasing temperature and time, indicating the improved contact in the interface between unreinforced Al-Mg part and Al-Mg/SiCp composite part. The relative density in the bi-materials increased as the sintering temperature and time increased, and the bi-materials sintered at 1173K for 5h showed the highest density.

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