A calorimetric analysis of the precipitation reactions in AlSi1MgMn alloy with Cu additions

The DSC spectrum of the AlSi1MgMn alloy with 0.05 wt% Cu confirms the well established precipitation sequence for ternary Al-Mg-Si alloys: supersaturated solid solution → GP zones → β″ → β′ → β. The precipitation activities are displaced to lower temperatures with increasing Cu concentration. Additional Cu-bearing metastable precipitates, L, Q and θ, are evidenced by the change in the peak configuration in the DSC spectra of Cu-added AlSi1MgMn alloys. The following precipitation sequences; SSSS → GP → θ′ → L → β″ → Q′ → β′ → β/Q/θ and SSSS → GP → θ″ → θ′ → L → β″ → β′ → β/θ offer a plausible account of the revised peak configurations in the DSC spectra of the AlSiMgMn alloy with 0.15 wt% Cu and with at least 0.3 wt% Cu, respectively.