Two-step aging behaviors of Al-Mg-Si alloy extrusions

Abstract

The two-step aging behaviors of various Al-Mg-Si alloy extrusions have been studied mainly by tensile testing, differential scanning calorimetric analysis (DSC) and electrical resistance measurements. The natural aging at 5°C, 20°C and 40°C for 86.4 ks has a beneficial effect on the strength after artificial aging of the low Mg2Si containing alloys. On the other hand, the natural aging has a negative effect on the strength after artificial aging of the high Mg2Si containing alloys. The β″ peak on the DSC curve shifts to a higher temperature with natural aging for the high Mg2Si alloy. However, no β″ peak was found for the low Mg2Si alloy. This suggests that there is no negative effect dominated by β″ phase for the lower Mg2Si alloys.