The effect of cold working on Hf solute clusters in CuHf as studied by time differential perturbed angular correlation (TDPAC) and positron lifetime measurements

The presence of Hf solute clusters in a Cu matrix has been identified by time differential perturbed angular correlation (TDPAC) studies and further confirmed by energy-dispersive x-ray analysis. Cold working of the CuHf sample results in a strain at the Hf solute clusters as deduced from the TDPAC. Annealing treatments of the sample lead to the restoration of the strain-free nature of the solute clusters. A defect associated with a 0.06 fraction of probe nuclei which is stable up to 925 K is interpreted as a faulted dislocation loop. Positron lifetime measurements on the cold-worked sample indicate the presence of a single lifetime component which is interpreted as due to the annihilation of positrons predominantly at dislocations, faulted dislocation loops and in addition at misfit dislocations at the interface between the Hf solute clusters and the matrix. (author)