MECHANISMS OF RADIATION-INDUCED SEGREGATION IN DILUTE NICKEL-ALLOYS

Measurements of the redistribution of several solutes in 75 keV self-ion irradiated dilute nickel alloys are described. The segregation is induced by the flow of irradiation-produced point defects out of a layer centred at 20 nm depth. It is concluded that Al, Cr and Mn dissolved in nickel exhibit negligible binding to vacancies and segregate by relatively rapid exchange with vacancies (the inverse Kirkendall effect), as does Ti above 400°C, but below this temperature a bound mobile Ti/vacancy complex forms. Below 100°C, segregation of a solute towards the surface is ascribed to the action of the interstitial flux. Silicon segregates by the formation of bound mobile Si/defect complexes. Evidence is presented that at least two different complexes are important above 400°C. © 1979.