Microstructural evolution of Alloy 718 at high helium and hydrogen generation rates during irradiation with 600-800 MeV protons

When precipitation hardened Ahoy 718 is irradiated with high-energy protons (600-800 MeV) and spallation neutrons at temperatures below similar to 60 degreesC, it quickly hardens and roses almost all uniform elongation. It la ter softens somewhat at higher exposures but does not regain any elongation . This behavior is explained in terms of the evolution of Frank loop format ion, disordering and eventual dissolution of the gamma' and gamma " strengt hening phases, and the steady accumulation of very large levels of helium a nd hydrogen. These gases must be dispersed on a very fine scare in the matr ix since no cavities could be found. (C) 2000 Elsevier Science B.V. All rig hts reserved.