Positron and transmission electron microscopy study of precipitation phenomena in an Al[sbnd]Li[sbnd]Zr alloy

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Abstract
Positron annihilation spectroscopy has been used to follow the precipitation processes in an aluminium alloy containing 12.5at.% Li and 0.04at.% Zr. Complementary techniques such as optical and electron microscopy and micro-hardness have also been used to characterize the samples. From the data it is confirmed that positrons are trapped at the δ′ precipitates and is inferred that they are extremely sensitive to the presence of interfaces associated with the precipitates, which allows precipitation and particle coarsening processes to be followed. The microhardness evolution by ageing at 423 K is consistent with the interpretation of the lifetime results.