Al–Mg–Si合金のベークハード性に及ぼすMgとSi添加量および自然時効の影響

抄録

Effect of natural aging conditions on split aging, especially bake hardenability at 170°C for 1.2 ks and 86.4 ks on Al–1%Mg₂Si, Al–1.5%Mg₂Si and Al–1%Mg₂Si–0.6%Si alloys have been studied using hardness measurement, DSC analysis and electrical resistance measurement. The increasing hardness of an Al–Mg–Si alloy with excess Si during baking at 170°C for 1.2 ks without natural aging is higher than that of Al–Mg–Si alloys without excess Si. However, the hardness of the high Si content alloy after baking at 170°C for 1.2 ks was decreasing with increasing natural aging time before baking clearly. It could be considered that the cluster which did not transfer to β″ phase formed using vacancy during natural aging on the high Si content alloy. The β″ phase of the high bake hardenability sample on DSC analysis appeared at lower temperature compared with the low bake hardenability sample. The β″ phase which was located at lower temperature on DSC analysis precipitates quickly during bake at 170°C, and the hardness was increased during baking at 170°C for 1.2 ks.