O. Celik, I. Dagli, M. Baydogan, E. S. Kayali, H. Cimenoglu, Istanbul Technical University, Istanbul, Turkey

Summary:

Age hardenable aluminium alloys are attractive materials for aerospace and aeronautical industries due to their improved strength to weight ratio. Even though they show good resistance to degradation in some corrosive environments, they often suffer from failures due to corrosion and/or synergistic attack of corrosion and wear in some aggresive media. The most common types of corrosion found on aircraft structures are pitting corrosion, intergranular corrosion and stress-corrosion cracking.

This study aims to compare the intergranular corrosion, dry sliding wear and corrosive wear responses of 3 mm thick 7175 aluminium alloy after conventional aging (T6) and retrogration and reaging (RRA) treatments. RRA treatments were applied in two sequential steps, namely retrogression and reaging, following T6 treatment. Retrogration step was carried out at 220, 240 and 260 °C. Then the alloys were reaged at 120 oC for 24 h. Corrosion and corrosion wear tests were conducted in two different solutions (30 g/l NaCl + 10 ml/l HCl and 57 g/l NaCl +10 ml/l H₂O₂). Among the examined retrogression temperatures, 260 °C yielded the best corrosion resistance. When compared to the T6 treatment, RRA treated alloy retrogressed at 260 °C tended superior corrosion and dry sliding wear resistance. However RRA treated alloy showed lower corrosion wear resistance than T6 treated alloy.