Shear punch testing of 59Ni isotopically-doped model austenitic alloys after irradiation in FFTF at different He/dpa ratios

In this last of a series of papers describing the evolution of microstructure, void swelling and mechanical properties of model austenitic alloys in response to differences in helium/dpa rates, shear punch testing is used to assess the relative effect of helium generation ratios and various important material and environmental variables. Shear punch data confirm the general trends observed in earlier tensile data derived from the Ni-59 isotopic doping experiment. There is a convergence to a common saturation level of yield strength that depends on alloy composition, temperature and displacement rate, but not on starting condition. The approach to saturation can be sensitive to helium/dpa ratio, however, and may depend on the starting state. For reasons not yet known, shear punch tests appear to be more sensitive to such transient differences than are tensile tests. (C) 1998 Published by Elsevier Science B.V. All rights reserved.