Effects of heavy-ion irradiation on the morphology of γ/γ' alloys

Nickel-ion irradiation of a two-phase γ/γ' Ni--Al alloy is shown to accelerate coarsening at low doses and to cause changes in γ' size, shape, and distribution at higher doses. The former results from irradiation-enhanced diffusion, whereas the other three changes are shown to originate from the interaction of γ' with the dislocations that develop during irradiation. At 5500C and a damage rate of 2.7 x 10-3 dpa/s, the γ' approaches a stable or steady-state mean diameter of approximately 85 A. This, in contrast to previous work, is shown to result from the balance between irradiation-enhanced coarsening and particle fragmentation due to dislocation cutting. Dislocation loops that develop early in the irradiation cause and are centered at regions devoid of γ'. Microstructural features produced by different irradiation conditions can be understood in terms of these mechanisms