Modulation of the natural aging effect on subsequent artificial aging in Al–Mg–Si aluminum alloys with alloying content ∼ 1 wt% through temperature tuning

In this paper, the influence of the natural aging (NA) on the subsequent artificial aging (AA) process in Al–Mg–Si aluminum alloys with alloying content ∼1 wt% was studied. Methods including various aging, hardness testing, transmission electron microscope (TEM), atom probe tomography (APT) etc, were employed. The results show that the NA before AA affects the AA precipitation process adversely under lower AA temperatures, e.g. 150 °C, by suppressing the peak aging hardness, while such effect can be modulated to be positive by increasing AA temperature to over 175 °C. Under higher AA temperatures, transformation of clusters into main strengthening precipitates, β″ phase for example, is promoted. The nucleation probability of these phases is enhanced, through lowering the nucleation energy barrier. As a result, the NA clusters facilitate nucleation and growth of the main precipitates during AA. The overall results proved that the NA effect on the subsequent AA process in the Al–Mg–Si aluminum alloys with alloying content about 1% can be modulated by tuning the AA temperature.