Ta-181 time differential perturbed angular correlation (TDPAC) and positron
lifetime measurements were carried out on homogeneously alpha-implanted Cu
Hf samples. TDPAC measurements indicate the trapping of vacancy clusters an
d helium associated defect complexes by Hf atoms. The presence of helium-va
cancy complexes and helium stabilised voids has been identified by positron
lifetime measurements. Further the nucleation and growth stages of helium
bubbles have been identified. TDPAC and positron lifetime measurements indi
cate that Hf atoms act as heterogeneous nucleating centers for helium bubbl
es. Hf atoms are found to suppress the bubble growth in CuHf as indicated b
y the results of positron lifetime measurements.