MICROSTRUCTURE AND CREEP IN NI(AL) ALLOYS UNDER PROTON IRRADIATION

Irradiation-induced creep under 6.2 MeV proton irradiation at temperatures of 433, 573 and 663 K was studied in solution-hardened Ni-8.5 at% Al and Ni-11.1 at% Al alloys, and in Ni-13.1 at% Al alloys in a solution-hardened and in various precipitation-hardened conditions. The irradiation creep rates slightly decreased with increasing Al content but were insensitive to pretreatment. The creep rates were similar to those of other solution-hardened Ni alloys and austenitic FeCrNi alloys. In the solution-annealed 13.1 at% alloy γ′-precipitation occured during irradiation, while in pre-aged specimens the coarse precipitates were gradually dissolved and small precipitates appeared. The dislocation structure in cold-worked specimens recovered at very small doses and dislocation loops appeared. In the solution-annealed specimens these loops were always found in precipitation-free area, while in the pre-aged material loops and dislocations were mostly attached to the coarse precipitates. The irradiation creep rates and the growth rates of loops and precipitates are quantitatively modelled by rate equations.