Influence of Li in deformed Al-Li alloys

Positron-annihilation Doppler-broadening and lifetime measurements are used to study the influence of Li on the defect behavior in deformed Al--0.2 at. % Li and Al--9.9 at. % Li samples. Deformations were performed at low temperature (77 K) and at room temperature. For the low-temperature deformed sample the migration and subsequent clustering of vacancies is seen in a stage between 200 and 350 K. The temperature dependence of the positron trapping rate at voids is seen. Above this annealing stage the only remaining defects are dislocations that anneal out above room temperature. In the dilute alloys it is seen that these dislocations are pinned by the Li atoms. In the concentrated alloy trapping of positrons at the {δ}' particles is observed. In the room-temperature deformed dilute alloys vacancy-Li complexes and dislocations are formed. These defects anneal in two distinct stages.