Enhanced radiation tolerance of YSZ/Al2O3 multilayered nanofilms with pre-existing nanovoids

Utilization of high density small sinks, such as voids, to collect and store helium atoms inside might be a potential new strategy for designing nanostructured materials with high radiation resistance to swelling and embrittlement. To understand the role of pre-existing nanovoids on irradiation, we investigated the evolutions of micro-structure and mechanical properties of the YSZ/Al2O3 multilayered nanofilms irradiated by He ions to different fluences. Compared to the Al2O3 monolithic film and the single crystal bulk YSZ, smaller He bubbles were found in the Al2O3 layers of the YSZ/Al2O3 multilayered nanofilms with pre-existing nanovoids after He ion irradiation. The growth of He bubbles was restricted inside the Al2O3 layers to avoid the formation of large bubbles. In contrast to the radiation-induced hardening in traditional materials, radiation-induced softening is observed in the YSZ/Al2O3 multilayered nanofilms with pre-existing nanovoids irradiated to high fluences. In addition, the hardness to Young's modulus (H/E) ratio of the YSZ/Al2O3 multilayered nanofilms increases in response to irradiation, which suggests a potential improvement in the wear resistance of the irradiated YSZ/Al2O3 multilayered nanofilms. A defect loading-unloading effect at the interfaces was proposed to explain the enhanced radiation tolerance. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.