Effects of grain structure related precipitation on corrosion behavior and corrosion fatigue property of Al–Mg–Si alloy

An Al–Mg–Si alloy with three types of grain structure (fully, partly, and none recrystallized grains) were prepared to determine the effects of grain structure related precipitation on corrosion resistance and corrosion fatigue property in this paper. Corrosion immersion tests, corrosion fatigue tests were conducted for the purpose. Through the investigations, a mechanism different from the existent mechanisms for expounding the corrosion behavior of Al–Mg–Si alloys is proposed in this paper. It was found that low angel grain boundaries (LAGBs) with continuous Mg-Si segregation play a dominant role on the penetration depth of corrosion; while the intragranular dislocations induced precipitates determine the corrosion morphology on the surface of the sample; in addition, the high angel grain boundaries (HAGBs) and precipitation free zones (PFZs) in the periphery do not decrease the corrosion resistance of the experimental alloy in the conditions of this paper. Furthermore, a deeper penetration of corrosion rather than the severer attack of corrosion on the surface results in a shorter corrosion fatigue life, as well as a corrosion dominated fracture failure during corrosion fatigue tests.These results may supplement the existing corrosion mechanisms of Al–Mg–Si alloy.