POSITRON AND TRANSMISSION ELECTRON-MICROSCOPY STUDY OF PRECIPITATION PHENOMENA IN AN AL-LI-ZR ALLOY

Positron annihilation spectroscopy has been used to follow the precipi tation processes in an aluminium alloy containing 12.5 at.% Li and 0.0 4 at.% Zr. Complementary techniques such as optical and electron micro scopy and microhardness have also been used to characterize the sample s. From the data it is confirmed that positrons are trapped at the del ta' precipitates and is inferred that they are extremely sensitive to the presence of interfaces associated with the precipitates, which all ows precipitation and particle coarsening processes to be followed. Th e microhardness evolution by ageing at 423 K is consistent with the in terpretation of the lifetime results.