Influence of Mg, Ag and Zn minor solute additions on the precipitation kinetics and strengthening of an Al-Cu-Li alloy

The influence of minor solute additions of Mg, Ag and Zn and their combinations on the precipitation kinetics and strengthening of an Al-Cu-Li alloy has been systematically investigated. Combining differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) provides information on how alloy chemistry changes the precipitation sequence, the precipitation kinetics in non - isothermal and in isothermal conditions, and the related strengthening. When adding Mg, the precipitation kinetics are strongly accelerated, which is shown to be related to the dominant formation of T1 precipitates. When adding Ag and Zn together with Mg, further enhancement of precipitation kinetics is observed, without change of the precipitation sequence, probably due to a more efficient nucleation of T1. The intrinsic strengthening potential of the T1 phase is shown to be unchanged by the addition of Ag and Zn, and the higher strength reached in the alloys containing these additions is shown to be due to a higher precipitate volume fraction.

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