Some observations on microstructural damage produced by fatigue of an aluminium-7.5% zinc-2.5% magnesium alloy at temperatures between room temperature and 250°c

摘要: Abstract Fatigue damage in an aluminium-7.5 % zinc-2.5 magnesium alloy has been studied using optical and transmission electron microscopy. Persistent slip bands, observed microscopy on test pieces eleetropolished after torsional fatigue at room temperature, were found by to be regions of precipitate re-solution up 500A wide. With increase testing although the initial was again re-solution, there increased tendency for precipitation occur during dislocation arrays, both within persistent bands oil interfaces between matrix. This resulted progressive overageing temperatures above 150°C. Increase temperature 200°C produced grain boundary crack initiation, intercrystalline zones formed, similar metallographic appearance bands. cracks fatigued 250°C matrix, where coarse precipitates had formed arrays. When failure occurred, associated with damaged