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DVRC 분석에 의한 A1-고농도 Mg (7 ~ 11 wt%) 합금의 석출분해 과정의 해석
정동석,박수동 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.1
Utilizing electrical resistivity measurements during heating, precipitation behaviors of high Mg contented Al-Mg alloys, which is currently spotlighted as automotive sheet material, has been analyzed. In the attempt to analyze precipitation behavior in detail, electrical resistivity change ratio was differentiated by temperature and acquired DVRC (Differentiation values of electrical resistivity changes). By measuring DVRC during heating, more precise analysis was possible than conventional electrical resistivity measurement. The transformation process of precursor phase, such as G. P. zone, shown as positive peaks at low temperature region in DVRC, was accelerated by higher solid solution treatment temperature. This reaction was identified as being activated by excessive vacancy concentration. With increased heating rate and Mg addition, splitting of DVRC peaks in low and high temperature was observed. This indicates that in high Mg concentrated Al-Mg alloy various precipitation processes highly depend on heating rate and Mg concentration.
조현기,은일상,유병호,박수동,백정우 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.8
For the purpose of ameliorating of toughness by boundary control, Be was added to Al-Li multiphase alloys. Interface behaviors during ageing were investigated by means of the measurements of hardness and tensile strength, and also the observation of optical and transmission electron micrographs. In order to evaluate the fracture toughness, instrumented Charpy impact test was carried out and fracture surface was observed with a scanning electron micrograph. Grain size was refined by α-Be particles that acted on dragging force at grain boundary in Al-Li-Cu-Be alloy. And PFZ half width in Al-Li-Cu-Be alloy was decreased by early precipitation of T₁ phases compared with Be-free alloy. Double eak phenomenon which was observed at the hardness and tensile tests in Al-Li-Cu-Zr-Be alloy may be estmated by the precipitation of secondary T₁ phases due to the change of δ′, T₁ and θ′ phases stability. And considering toughness and elongation, it is possible to think that the secon peak condition may be the most optimum condition of heat treatment because of the remarkable improvement of elongation in Al-Li-Cu-Zr-Be alloy. In case of Al-Li-Cu-Zr alloy containing minor Be, higher impact absorbed energy than that of Be-free alloy was observed. This remarkable improvement of fracture toughness was attributed to the change of fracture mechanism from brittle to ductile mode. the high energy fracture mode of minor Be added alloy was associated with homogeneous deformation due to various interface controls.