Effects of heavy-ion irradiation on the phase stability of several copper-base alloys

The radiation-induced precipitation in a binary Cu-3.4 at. % Be alloy under various radiation conditions has been characterized. The alloy specimens were irradiated with 14 MeV Cu ions, which produced depth dependent displacement damage extending to a depth approx. 3000 nm from the specimen surface. At a depth of 1000 nm, displacement damage ranged from 0.25 to 10 dpa, at damage rates of approx. 10-3 dpa/sec. Irradiation temperatures ranged from 300 to 5250C. Specimens were irradiated in both the solution-annealed and thermally-aged condition. The microstructure of irradiated and non-irradiated specimens were examined using a transmission electron microscope. Irradiation of supersaturated solid solutions of the alloy at temperatures of 300 to 4000C to damage levels as low as 0.1 dpa induced continuous precipitation of CuBe platelets, whose morphology was similar to #betta# platelets observed during the thermal aging of more concentrated Cu-Be alloys. The precipitate dissolved during post-irradiation annealing even at a temperature (4000C) within the two-phase region of the equilibrium phase diagram. Prolonged thermal aging near this temperature produced coarse discontinous precipitation at grain boundaries and in clusters within the grains. The unsaturated solid solution dissolved during irradiation at somewhat higher temperatures. Irradiation of two other simple alloys, Cu-1% Co and Cu-1% Fe, at 350 to approx. 5000C was noted to produce mainly a loss of precipitate coherency. In cross-sectioned alloys, coherency loss was noted well beyond the end of the ion-penetration range