Advanced positron annihilation studies of CuCrZr alloys

Abstract

The influence of heat treatment (HT) on precipitate sizes and densities in CuCrZr alloy has previously been investigated by transmission electron microscopy (TEM). In this work, we studied the effect of HT on the defect structure in non-irradiated CuCrZr alloy using positron annihilation spectroscopy (PAS). Results obtained by PAS were compared with the results achieved by TEM. In the PAS measurements, a precise-defined long defect lifetime τ2 was observed with a basically constant value, while its intensity I2 exhibited strong dependency on the HT. Thus, a clear influence of the applied HT on the defect microstructure of CuCrZr alloy was observed. The measured defect lifetime τ2 parameter was associated to the creation of the vacancy-type defects at the precipitate matrix interface. We assume that it arises from the lattice mismatch (matrix, dislocations and precipitates). Further, the dependency of the specific trapping rate on the precipitate radius rppt was estimated and compared to theoretical values based on the diffusion-limited trapping and transition limited trapping models. These results are the base for future detailed studies of CuCrZr alloys after fast neutron irradiation treatment in connection to development of ITER or GenIV suitable materials.