EARLY STAGES OF IRRADIATION INDUCED GAMMA-' PRECIPITATION IN PROTON IRRADIATED NICKEL-SILICON ALLOYS

The early stages of irradiation induced precipitation of γ' in undersaturated Ni-Si alloys containing 2, 4, 6 and 8 at.% solute have been studied in samples irradiated by 400 keV protons to doses of 0.13 and 0.25 dpa at a dose rate of 2.37 × 10-5 dpa/s over the temperature range 400 to 600°C. Despite the low doses used, substantial solute segregation has been observed, as evidenced by the presence of irradiation induced γ' at voids in many of the samples containing 2 and 4 % Si, and by what appears to be discontinuously precipitated γ' at grain boundaries in some of the 8% Si alloys. Also, we have observed, for the first time, irradiation induced coherent γ' precipitates in the 6 and 8% Si alloys at the highest irradiation temperatures. These effects are discussed in the light of recent theories of irradiation-induced solute segregation and precipitation. © 1979.