Oxidation induced void formation in TEM specimens of Al-Cu-Li alloy

A TEM study has revealed, for the first time, the presence of small (similar to 3 nm in diameter) voids attached to T(1) (Al(2)CuLi) precipitates present in an artificially aged Al-Cu-Li alloy (Al-2.90Cu-1.63Li-0.29Mg-0.28Ag-0.13Zr). These voids do not form from quenched in excess vacancies but are nucleated at the T(1) phase/alloy interface from excess vacancies generated during oxidation of the TEM sample. It is concluded that these voids result from the Kirkendall effect with rapid oxidation of the TEM metal surface occurring by molecular oxygen migration through a highly defective surface oxide layer.