| 摘要 |
PROBLEM TO BE SOLVED: To improve corrosion resistance by specifying the atom composition. SOLUTION: This alloy is composed of 3 to 10wt.% Si, 0.7 to 4wt.% Mg, and the balance Al, and formed of an aluminum having the dendrite structure and an eutectic consisting of anαsolid solution and an eutectic Si. Then, the Mg density inside the aluminum is made as 0.5 to 1.5wt.%. Thus, the corrosion resistance is improved by the following reason. The impurities are easily collected inside theαsolid solution, then the corrosion voltage is lower in comparison with the aluminum, besides, the voltage of the eutectic Si is largely high. Theαsolid solution existing on the boundary of the eutectic Si and the aluminum is corroded selectively. Then, when the Mg density inside the alloy is increased, the Si inside the solid solution forms Mg2 Si, and is solid-solved in theαsolid solution or the aluminum, or deposited inside the eutectic ground. Consequently, the corrosion voltage of theαsolid solution is raised, the difference of corrosion voltage with the circumferential aluminum ground or the eutectic Si is made small and the corrosion rate is made gentle.
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