抄録
The aging behavior of Al-10%Si-Mg system alloys cast into sand mold were investigated by optical microscopy, scanning electron microscopy and micro-vickers hardness measurement. The castings were demolded and water-quenched at 323, 473, 573, 673 and 773K after cast, and then those were artificial aged at 423, 473 and 523 K. With increasing Mg content from 0.3 % to 0.9 %, the agehardenability (ΔHV: difference of hardness between as-cast and peak-aged condition) was increased relatively gradually, because the solid solubility of Mg and Si in the matrix was decreased due to the crystallization of π-Fe and Mg2Si phases. The ΔHV of sand mold castings was larger than that of permanent mold castings when the demolded temperatures were 673 K and 773 K. This is due to the difference in the amount of precipitates, which were attributed from passing time at high temperature range above solvus line of metastable Mg2Si phase.
