Study on thermal stability and irradiation response of copper/iron nano-multilayer composite fabricated by cross accumulative roll bonding

Abstract Nano-multilayer composites simultaneously exhibit high strength and good radiation resistance because of its huge density of interfaces. However, such outstanding behaviors are influenced by their thermal stability. In this study, we investigated the evolution of microstructure and hardness in Cu/Fe composites fabricated by cross accumulative roll bonding (CARB) with different individual layer thicknesses and annealing time. The results demonstrated that the composites with a layer thickness of 90 nm are more resistant to layer pinch-off and spheroidization, and maintain a relatively high strength after the long-time annealing at 400 °C. By contrast, the decreasing Cu/Fe interface density and severe grain spheroidization in the 30 nm sample lead to a significant drop in hardness. Furthermore, as for helium irradiation response in the 90 nm Cu/Fe composite at 500 °C, some columnar voids with a large aspect ratio appear at Cu/Fe interfaces, demonstrating that void elongation in the normal direction of the interface requires to satisfy both kinetic (along vacancy flux) and thermodynamic (along {111} plane) factors. In addition, the obviously increasing bubble size mainly contributes to the hardening in Cu/Fe multilayers after high-temperature irradiation.