The stress relief is accomplished by stretching the metal by an amount that depends on the type of standard wrought product being made (sheet, plate, bar, or forging).
The graph bars on the material properties cards below compare 7075-T651 aluminum to: 7000-series alloys (top), all aluminum alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
With zinc as the dominant alloying element, the 7075 aluminium alloy (also known as aircraft aluminium or aerospace aluminium) was the first alloy of high strength composed by Al-Zn-Mg-Cu that was able to successfully combine the perks of the inclusion of chromium to develop high stress-corrosion cracking resistance in sheet products. The composition of the 7075 aluminium alloy consists of 87.1 – 91.4% aluminium, while the zinc is present in a concentration of 5 – 6%. It also contains 2.1 – 2.9% magnesium, 1.2 – 2%, and no more than 0.5% of silicon, titanium, chromium, iron, manganese, and other constituting metals.
The 7075-T6 aluminium is a 7075 aluminium alloy with a T6 temper, which is achieved by treating it with solution heat, homogenizing the 7075 cast at 450 °C for several hours, quenching, and then artificially aging it at 120 °C for 24 hours, which is around the time when it meets standard property requirements. This process guarantees achieving the peak strength of this alloy.