Some Thoughts on Stress Corrosion Cracking of (7xxx) Aluminum Alloys

Abstract

: Stress corrosion cracking may be defined as a spontaneous failure of the metal resulting from the combined effects of corrosion and stress. It is general agreement that SCC requires three conditions: first, the alloy must be susceptible, second, there must be a specific environment (water or seawater for aluminium alloys); and third, there must be a tensile stress. The susceptibility of the wrought aluminium alloys to SCC is related to many environmental (chemical), Metallurgical (Microstructural) and Mechanical factors. Crack initiation may start at some surface discontinuities, corrosion pits, or may be developed by intergranular corrosion or slip dissolution. This review describes the models of environmental - related crack propagation of aluminum alloys (7xxx) during the last few decades. Acknowledge on effects of different factors on the susceptibility to SCC permits to propose valuable mechanisms on crack advancement. The reliable mechanism of cracking gives a possibility to propose the optimum chemical composition and thermal treatment conditions resulting in microstructure the most suitable for real environmental condition and stress state.