Dependence of void swelling on the electron vacancy concentration

Large variations were noted between the swelling of different iron, chromium, nickel alloys and suggestions were made that the differences are due to variations in the carbon, silicon, phosphorus, and nickel content of the alloys. Harries has postulated that variations in the solute concentration of the gamma matrix could be responsible for the different swelling behavior and that the formation of any second phase which leads to a depletion in the solute concentration will in turn lead to an impairment in swelling resistance. The swelling of several commercial alloys irradiated at 6000C (11120F) in the Dounreay Fast Reactor lend general support to Harries' suggestion and the swelling at 30 atomic displacements per atom (dpa) has been shown to increase with the calculated equilibrium fraction of sigma phase. A superior correlation was shown to exist between the swelling and calculated electron vacancy concentration of the matrix and a critical value of 2.58 electron vacancies per atom was observed above which swelling increases rapidly and below which swelling is small