Nickel and nitrogen ion irradiation induced void swelling and defect microstructures in Ni-Al, Ni-Cr and Ni-Ti solid solutions

Abstract

The effects of solute content, temperature, and irradiation dose on the void swelling characteristics of pure nickel and several nickel base solid solutions (Ni-Al and Ni-Ti containing up to 8 at. pct solute and Ni-Cr containing up to 16 pct Cr) have been iNvesti-gated. Samples were irradiated in the temperature range 400 to 650°C to a maximum dose of 70 dpa using 3.5 MeV58Ni+, 400 keV14N+ and 400 keV14N+ 2 ions. The irradiation in-duced microstructures were studied using transmission electron microscopy. In general, the addition of Al, Cr or Ti to Ni is found to decrease the void swelling and mean void diameter and to increase the dislocation density. The behavior of the void number den-sity, Nv, as a function of solute content is found to be dependent upon the irradiation con-ditions as well as the particular solute addition. Nv passes through a maximum at approxi-mately 2 pct solute content for Ni-AI and Ni-Cr alloys irradiated at 550°C, but through a minimum at 4 pct for Ni-Ti alloys irradiated at 550 and 600°C. Nv decreases monotoni-cally as a function of Al content at 600 and 650°C. The results are discussed in terms of recent theories of void swelling suppression due to impurity or solute additions and in light of several correlations between void swelling and material parameters. The be-havior of Nv is found to be best described by the actions of two compcting processes. The first enhances void nucleation, is not strongly temperature dependent and is dominant at low solute contents. The second suppresses void swelling, is probably diffusion con-trolled and dominates in the more concentrated alloys. © 1978 American Society For Metals and the Metallurgical Society of AIME.