Effects of pre-aging at elevated temperature and natural aging on the bake hardenability of Al-Mg-Si alloy

Abstract

Effects of natural aging before pre-aging, pre-aging and natural aging after pre-aging on the bake hardenability of the Al-0.62 mass% Mg-0.96 mass% Si alloy have been studied by tension test, hardness measurement, electrical resistance measurement and differential scanning calorimetric analysis (DSC). The bake hardenability after natural aging at 20°C for 86.4 ks was improved by pre-aging between 100°C and 170°C. In the case of short pre-aging at 100°C, the bake hardenability started to decrease after natural aging for more than 86.4 ks, because the amount of clusters of solute atoms increased. Natural aging before pre-aging causes decreasing the bake hardenability because the clusters formed during natural aging before pre-aging.