Time differential perturbed angular correlation (TDPAC) measurement on <(Al
)under bar>Hf reference sample has shown that a fraction 0.88 of probe nucl
ei are defect free and are occupying the substitutional sites in fee Al mat
rix, and the remaining are associated with Hf solute clusters. Measurements
on helium implanted sample indicate the binding of helium associated defec
ts by Hf solute clusters. Isochronal annealing measurements indicate the di
ssociation of the helium implantation induced defects from Hf solute cluste
rs for annealing treatments beyond 650 K. On comparison of the present resu
lts with that reported in <(Cu)under bar>Hf subjected to identical helium i
mplantation, it is inferred that the Hf solute clusters in <(Al)under bar>H
f bind less strongly the helium associated defects than in <(Cu)under bar>H
f.