| 초록 |
Al-Si-Mg alloys are investigated to determine the relation between change of thermal diffusivity and precipitation behavior of the Mg2Si phase with various contents of Mg2Si and aging treatment condition. The samples were solid solution treated and then quenched with water (80 ºC). Aging treatments were implemented at the temperature range from 180 to 240 ºC for 5h. The precipitation behavior of Mg2Si was observed from a heat flow curve of difference scanning calorimetry (DSC) analysis and change in the coefficient of thermal expansion curve. The thermal diffusivity of Al-Mg2Si alloy was affected by precipitation of the Mg2Si phase, especially in the meta-stable β phase. In the temperature range of precipitation occurrence, the thermal diffusivity of alloy was increased with temperature when precipitation of the meta-stable β phase of the sample was incomplete, regardless of the amount of Mg2Si. However, at the same temperature, the samples in which precipitation was completed did not have an increased region of thermal diffusivity. In addition, the thermal diffusivity of samples changed when the meta-stable Mg2Si phase had dissolved in the matrix. When the Mg2Si had dissolved with the Mg and Si atoms, both shrinking of the lattice and decrease of thermal diffusivity occurred. The precipitation and dissolution of Mg2Si mainly affected the variation of the thermal diffusivity in Al-Si-Mg. On the other hand, the stable Mg2Si phase was not affected by the thermal diffusivity change at the high temperature. |
