Positron lifetime and perturbed angular correlation measurements of the annealing of quenched Al and dilute AlIn alloys

Positron lifetime and perturbed gamma gamma angular correlation (PAC) measurements are used to compare the annealing of pure Al and dilute AlIn alloys, quenched from 650 K. After quenching, the formation of vacancy clusters as well as single vacancy-In atom and divacancy-In atom complexes is observed. During quenching of all samples the vacancy-vacancy interactions dominate the vacancy-In atom interactions. The single vacancy-In atom pairs disappear around 250 K because they either dissociate or migrate as a unit; in contrast, the divacancy-In atom pairs are converted into larger clusters at around 250 K. The presence of 22 p.p.m. In stabilises the three-dimensional vacancy clusters, so they do not disappear between 270 and 300 K, as observed by positron annihilation for pure Al, but persist up to 450 K. For this alloy, In-rich vacancy clusters are seen by PAC around 300 K, and continuous precipitation of In atoms is observed by positron lifetime measurements from 300 to 450 K.