Grain growth stagnation and texture development in an irradiated thermally stabilized nanocrystalline alloy

Abstract

Nanocrystalline metals are of strong interest in nuclear material applications because their grain boundaries may act as effective recombination sites for point defects. Consequently, they may be able to sustain high doses with minimal damage. Here, we investigate nanocrystalline NiW, a thermally stabilized nanocrystalline material with an initial grain diameter of 6 nm. We find that grain growth when subject to moderate doses of Ni+ self-ion irradiation is not distinguishable from that of nanocrystalline Ni. However, once the grains grow to an average diameter of 32 nm at 10 displacements per atom (dpa), this irradiation-induced grain growth (IIGG) stagnates up to 100 dpa. Such stagnation is not predicted by previous models. IIGG stagnation is found to correlate with microstructural evolution, where an initial weak fiber texture transforms into a biaxial texture with a concurrent increase in low energy grain boundaries acting to stabilize the microstructure at higher irradiation doses.