DEFECT ANNEALING AND THE FORMATION OF LI-RICH CLUSTERS IN AL-LI ALLOYS

Positron annihilation lineshape measurements are conducted on pure Al, Al-1.9 at.% Li and Al-(12.0-12.5) at.% Li alloys. The recovery of eac h sample following quench and/or cold-work treatments is discussed in terms of vacancy migration and clustering, dislocation annealing and p recipitation. The results indicate precipitation in both alloy concent rations but no positron trapping at dislocations. All cold-worked allo ys show large vacancy clustering effects, providing strong evidence of vacancy agglomeration at precipitates.