A study on the competition and synergy between irradiation and temperature on the texture and recrystallization of nanocrystalline nickel

Abstract

The application of nickel coatings on structural materials in molten salt reactors for corrosion resistance is being researched. For corrosion resistance, the coatings must have specific texture and grain boundary characteristics that withstand irradiation. While most reported results concern textural changes caused by room-temperature irradiation, research in the thermally-assisted regime, which is the operating temperature range of nuclear reactors, is limited. In this study, we investigate the effect of 1.4 MeV Ni+ ion irradiation on the texture, recrystallization, and grain boundary characteristics of nanocrystalline Ni at temperatures ranging from 250 °C to 550 °C. Thermal activation at 350 °C and 450 °C results in partially and fully recrystallized microstructures, respectively. A concurrent decrease of <100>//ED and evolution of <111>//ED, as well as minor orientations that reduces surface energy, are detected up to 450 °C; nevertheless, textural reversal is found at higher temperatures. Irradiation accelerated the recrystallization kinetics, resulting in a fully recrystallized microstructure at temperatures 100 °C lower. Irradiation at temperatures above 350 °C increased the thermally-induced texture; at 250 °C, this trend reversed. Calculated radiation-enhanced diffusion (RED) coefficients at 250 °C revealed that ion mixing drives the growth of <100> by consuming <111> orientations. Conversely, the increasing RED contribution at higher temperatures strengthens the thermally-induced textures.