Effect of Interrupted Ageing on Stress Corrosion Cracking (SCC) Behaviour of an Al-Zn-Mg-Cu Alloy

AbstractAn Al-Zn-Mg-Cu alloy is aged at 120°C for varying time and the peak hardness (T6) is found at 24h. A multi-step ageing was adapted to produce interrupted aged (T6I6) temper. Stress corrosion cracking behaviour of T6 and T6I6 tempers has been studied by slow strain rate test at free corrosion potential (FCP) and at applied anodic potentials in 3.5wt.% NaCl solution. T6I6 temper exhibited higher SCC resistance than T6 temper at FCP, but both tempers are damaging at applied potentials. TEM microstructures, SEM fractographs and crack morphology are used to analyze SCC behaviour of the alloy tempers