Internal friction associated with δ′ precipitation in Al–Li alloys

The anelastic behaviour of Al–Li alloys is studied in the temperature range between room temperature and 400 K. The internal friction technique is shown to be very sensitive to the microstructural changes that take place at these temperatures. A low-temperature shoulder (LTS) that appears from 270 to 400 K in the first heating run, is attributed to the growth of δ′ precipitates during heating. The experimental behaviour of the internal friction spectra under different microstructural and experimental conditions allows one to attribute this LTS to the stress-induced Li–Li reorientation process, similar to the Zener effect, but in an unstable microstructural situation where small δ′ precipitates are present.