The effect of γ irradiation on the creep properties of GH33A

a high temperature Ni base alloy

is investigated Creep curves

positron lifetimes and Doppler broadening spectra are measured The results show that plasticity of the non magnesium sample is greatly increased （38 1%） after irradiation

while the breaking lifetime keeps constant However

both lifetime and plasticity for the Mg containing （0 0045wt%） sample are reduced After negative creep load

lifetime of the irradiated non Mg sample increased （9 4%）

but plasticity decreased（25 6%） After irradiation and negative creep load

lifetime of the long aged alloy with Mg content of 0 0054% is increased significantly （48 3%）

while plasticity remain unchanged