| As-cast state of Al-7% Mg alloy was prepared by casting the melt into metallic mold. Then β-phase solution behaviors and mechanical properties of this alloy have been investigated. The activation energy of β-phase solution into matrix is about 25 ㎉/㏖, independent of β-phase content. This value is in good agreement with activation energy for diffusion of magnesium in Al-Mg alloy, and hence the solution process of β-phase is considered to be controlled by diffusion of magnesium in the alloy. Ultimate tensile strength increases linearly with decreasing β-phase content. Elongation, however, increases with decreasing β-phase content up to about 50%β, and then shows a nearly constant value, regardless of β content below 50% β. Impact toughness increases with decreasing β-phase content up to about 50%β, and then keeps a nearly constant value, irrespective of β content below 50% β, in the same way as was exhibited in the elongation. It is noted that the impact toughness shows a same value at the same level of β-phase content, irrespective of solution treatment temperature. |
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