Effects of Cu content and preaging treatments onprecipitation sequence and artificial aging response in aluminumalloy 6022 were investigated using transmission electronmicroscopy (TEM), differential scanning calorimetry (DSC), andhardness tests. It was found that Cu induces the formation of Qand its precursor metastable phases and has a beneficial effect onthe kinetics of artificial aging. For the alloy with 0.07 wt pct Cu,the precipitation sequence is GP zones -> needlelike #beta#" ->rodlike #beta#' + lathlike Q' -> #beta# + Si. On the other hand, theprecipitation sequence in the alloy with 0.91 wt pct Cu is GPzones -> needlelike #beta#" -> lathlike Q' -> Q + Si. For theartificial aging condition of 20 minutes at 175beg C, which is thetypical automotive paint bake condition, suitable preagingtreatments were found to significantly reduce the detrimentaleffect of the natural aging on artificial aging response.
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