Effect of Secondary Aging of AA7075 Aluminum Alloy to Hardness

Abstract

In this study, one of the major aluminum alloys AA7075 was held to obtain the maximum benefit for structural parts. Nowadays for the energy efficiency of vehicles like electric cars or aerospace vehicles weight reducing efforts are needed. To obtain lighter structures specific strengths are gaining importance. In our study, AA 7075 aluminum alloy was processed with additional heat treatment rather than T6 condition to obtain high strength. According to our previous studies, statistical methods seemed very useful to predict probable strength very precisely, for this reason, Box-Behnken Surface Response Method was used. By applying statistical methods, the artificial aging temperature and time were optimized. According to optimized temperature and time, the secondary aging heat treatment was done. In this study three T6 conditions 150, 200, and 250 oC with four treatment times, 1,2,4 and 6 hours were chosen and applied. The secondary aging temperature and time were obtained from Box-Behnken optimization study results and found as 182 oC and 2 hours were applied to all samples. As a result, after secondary aging heat treatment maximum hardness of 151 Hv was obtained from samples that aged at 150 oC, and 250 °C for 1 hour, which is almost doubled because the T6 aged sample has a hardness value of 86 Hv. This is obvious that the strength almost doubled, therefore it is possible to use sections almost half of the T6 condition samples.