The effect of microalloying additions of Au on the natural ageing of Al-Cu

The influence of microalloying additions of Au to the binary Al-Cu system is investigated utilizing hardness measurements, positron annihilation spectroscopy and X-ray absorption spectroscopy. No room temperature ageing could be observed in the case of the ternary Al-Cu-Au alloy. Instead, quenched-in vacancies were trapped by Au atoms and thus could not catalyse the decomposition of the alloy. However, artificial ageing dissolves the complexes of Au and vacancies. A comparison between experimental and calculated absorption spectra shows that Au atoms did not agglomerate significantly during either natural or artificial ageing.