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Vol.35, No.12, 1609 ~ 1616, 1997
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| Title |
| Precipitation Behavior of θand δ During Heat Treatment in Squeeze Cast Mg-Li-Al Alloys |
| 김영우 , 황영하 , 박태원 , 김도향 , 홍준표 Y . W . Kim , Y . H . Hwang , T . W . Park , D . H . Kim , C . P . Hong |
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| Abstract |
| Precipitation behavior of θ(MgLi₂Al) and δ(AlLi) in squeeae cast Mg-8.5wt%Li-4.5wt5Al has been investigated by scanning electron microscopy(SEM), differential scanning calorimetry(DSC) and in-situ and ex-situ X-ray diffraction analyis. Microstructural and calorimetric analysis of as-cast Mg-8.5wt%Li-4.5wt%Al shows that the temperature range required for the proper solution treatment is 370-400℃. Both θ and δ precipitate in the b.c.c. β phase matrix of Mg-8.5wt%Li-4.5wt%Al after solution treatment at 400℃, forming two exothermic peaks at the temperature range of 130℃-180℃ and 236℃-280℃ with the peak temperatures of 153℃ and 262℃, respectively. θ and δ dissolves into the matrix forming an endothermic peak at the temperature range of 280℃- 352℃. The as-cast microstructure consists of α, β wand δ. δ dissolves into the matrix after solution treatment. During aging treatment at 50℃-100℃ θ forms at the early stage of aging, and δ begins to form after completion of θ precipitation. Activation energies for the formation of θ and δ are 97.3㎉/mole and 111.7㎉/mole, respectively. |
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