The influence of heat treatments on electrical conductivity and corrosion performance of AA 7075-T6 aluminium alloy

Heat treatable aluminium alloys such as AA 7075 gains high strength during aging. These alloys have large applications in aircrafts, missiles and automobiles for many components. AA 7075 aluminium alloys is susceptible to exfoliation corrosion due to presence of high content of Zn. Different heat treatment processes are performed on age hardenable aluminium alloys to improve corrosion resistance. The objective of this study is to investigate the effect of different heat treatments such as retrogression and re-aging (RRA) and duplex aging on the corrosion performance and electrical conductivity of heat treatable AA 7075-T6 alloy. On coupons of AA 7075-T6 the retrogression at 200˚C for 2 hr and re-aging at 120 ˚C for 24 hr is performed. Also another treatment known as duplex aging at 163˚C for different time duration such as 4 hr, 8 hr, 16 hr, and 24 hr was performed. This was followed by exfoliation corrosion and the corrosion performance determined. The electrical conductivity is the most important measure associated with age hardenable aluminium alloys, which directly reflect the internal condition (microstructures) of such alloys. The study reveals that duplex aging at 163˚C for 16 hr shows better result for both electrical conductivity and corrosion resistance.