The Effect of Multi-Stage Age Treatment on Mechanical Properties of 7075 Al Alloy

Abstract

One of the widely used aerospace alloys is 7075 aluminum alloy (AA) because of its high tensile and compressive strength and good response to exfoliation corrosion. A solution heat treatment followed by artificial ageing is known as T6 temper designation was initially used to obtain peak strength for 7075 AA. The artificial aging, done at 115°C to 130°C (T6 temper), increases strength of 7075 AA to a peak level then decreases, however, resistance to stress-corrosion cracking is decreased. Recent trend shows that the strength can be increased more by applying multi-stage aging process. This research focuses on the effect of multiple aging temperature, time on the mechanical properties of 7075 aluminum alloys. ASTM standard coupons were machined from an as received aluminum plate and applied different combination of RRA age treatment. The initial results on mechanical properties are reported. The maximum tensile strength obtained was over 100 ksi for a double RRA at 200°C for 10 min. The hardness was measured using a micro hardness tester. The Vickers hardness numbers were within the range in literatures.