Defect microstructure in copper alloys irradiated with 750 MeV protons

Transmission electron microscopy (TEM) disks of pure copper and solid solution copper alloys containing 5 at% of Al, Mn, or Ni were irradiated with 750 MeV protons to damage levels between 0.4 and 2 displacements per atom (dpa) at irradiation temperatures between 60 and 200 degrees C. The defect cluster density in copper was observed to be constant for irradiation temperatures below about 130 degrees C, and to decrease with increasing temperature above 150 degrees C. About 60% of the defect clusters in copper were resolvable as stacking fault tetrahedra (SFT). Cavity formation was observed for irradiation temperatures above about 150 degrees C. The dislocation loop and network densities were relatively low in all of the irradiated pure copper specimens. Contrary to expectations, the loop density and size both decreased with increasing irradiation temperature. Solute additions did not have any significant effect on the total density of small defect clusters, but they did cause a significant decrease in the fraction of defect clusters resolvable as SFT to similar to 20 to 25%. In addition, the dislocation loop density (> 5 nm diameter) was more than an order of magnitude higher in the alloys compared to pure copper.