Grain size threshold for enhanced irradiation resistance in nanocrystalline and ultrafine tungsten

Nanocrystalline metals are considered highly radiation-resistant materials due to their large grain boundary areas. Here, the existence of a grain size threshold for enhanced irradiation resistance in high-temperature helium-irradiated nanocrystalline and ultrafine tungsten is demonstrated. Average bubble density, projected bubble area and the corresponding change in volume were measured via transmission electron microscopy and plotted as a function of grain size for two ion fluences. Nanocrystalline grains of less than 35 nm size possess similar to 10-20 times lower change in volume than ultrafine grains and this is discussed in terms of the grain boundaries defect sink efficiency. [GRAPHICS] . IMPACT STATEMENT A grain size threshold in nanocrystalline and ultrafine tungsten has been shown to exist for enhanced irradiation-resistance performance during high-temperature helium irradiation.