Effect of high-energy heavy-ion irradiation on the properties of copper

High-purity polycrystalline copper foils were irradiated with 233 MeV Ne and 443 MeV Ar beams with doses up to 5x1019 ion/m2. At high doses the yield stress, Δσy, approaches to saturation. TEM and electrical resistivity measurements show a monotonous increase of defect density with dose. Dislocation density obtained from X-ray diffraction is low and does not follow this trend. At a dose of 3x1019 Ne/m2 transformation of faulted Frank loops into perfect loops was deduced from TEM studies. The decline of the rate of increase of Δσy is connected with the softening of the obstacles to dislocation movement due to this transformation. (orig.)