The microstructures of two candidate high-strength, high-electrical conductivity copper alloys (AMZIRC and AMAX-MZC) have been studied after heavy ion irradiation and after thermal annealing. An investigation of the behavior of these alloys following thermal treatment has shown that much of their strength is due to cold-working (high dislocation density). Microhardness measurements revealed that the MZC and AMZIRC copper alloys have a recrystallization temperature of about 475°C. Both alloys have been irradiated with 14-MeV copper ions in the temperature range of 400 to 550°C (0.5 to 0.6 Tm). Samples were irradiated to maximum fluences of 3 × 1020 ions/m2, which corresponds to a calculated peak displacement damage of 15 displacements per atom (dpa) based on a damage efficiency of K = 0.3. The irradiated foils have been examined in cross-section with an electron microscope. No void formation was observed in either alloy for this temperature range. Irradiation was found to enhance dislocation recovery and grain recrystallization processes in both alloys at the lower temperatures. The observed results imply that the MZC and AMZIRC copper alloys may undergo a significant degradation in their mechanical properties when exposed to irradiation at temperatures around 400°C.