Microstructure and ultrasonic behaviour on thermal heat-treated Al–Li 8090 alloy

Ultrasonic velocity and attenuation measurements have been carried out on the as-received and thermally treated 8090 Al–Li alloys (T8771). Ultrasonic velocities, density and elastic moduli show a maximum at the thermally treated temperature of 463 K due to the influence of δ′ phase precipitation. The decrease in velocity beyond 463 K is associated with the initiation of dissolution of δ′ and δ phases and also the presence of small fraction of S′ phase. Overaging could be identified at 673 K from the changes in ultrasonic velocities and attenuation. The observed pronounced maxima in ultrasonic velocities and minima in attenuation at 470 and 593 K are associated with precipitation of δ′ and S′ phases, respectively.