Irradiation-induced creep (IIC) in dilute Cu-W nanostructured alloy films, 300 nm thick, was measured as a function of temperature during 1.8-MeV Kr + irradiation using plane-strain bulge testing. The creep rate increased with increasing temperature between 300 K and 473 K, and then became constant up to 573 K. An activation enthalpy of 0.30 ± 0.05 eV was obtained for Cu 93.5W 6.5 and Cu 99W 1 alloys. Thermal creep, in absence of irradiation, became comparable to IIC at 573 K. Primary and secondary creep were observed at all temperatures. The steady state creep rate was proportional to the applied stress. Subsequent (scanning) transmission electron microscopy analysis revealed a high density of small (2-3 nm) W-rich nanoparticles with BCC structure after irradiation at all temperatures, but no dislocation loops. The average grain size of the irradiated alloys was stabilized at ∼30-40 nm in both alloys. Correlations between the microstructures and creep behaviors are discussed in terms of grain boundary creep mechanisms.
Bibliographical noteFunding Information:
This research was supported by the US DOE-BES under grant DEFG02-05ER46217. It was carried out, in part, in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which are partially supported by the US Department of Energy under grants DE-FG02-07ER46453 and DE-FG02-07ER46471.