Abstract

Stress corrosion cracking (SCC) behavior of various retrogression and re-ageing treated, high-zinc (> 7 wt%) 7068 alloys is examined. SCC and inter-granular corrosion resistance is correlated with microstructural and compositional heterogeneities. Specimens that were pre-aged at 100⁰C and retrogression treated at 180 °C exhibited retarded reduction reaction kinetics in polarization studies, and better SCC resistance. Besides the microchemistry of grain boundary precipitates, matrix precipitate size affected the oxygen reduction kinetics. An increase in copper content of discontinuous boundary precipitates did not monotonously lead to improved SCC resistance. 7068 alloy specimens pre-aged at lower temperature exhibited higher strength and SCC resistance.

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