The effects of interfaces stability on mechanical properties, thermal conductivity and helium irradiation of V/Cu nano-multilayer composite.

[Display omitted] • Strength of V/Cu multilayer composites with smaller layer thickness degrades more drastically at high temperatures due to interface instability. • Spheroidization occurred in multilayer during the annealing process benefits the increase of thermal conductivity. • Different cavity morphology after high-temperature helium irradiation is related to defects diffusion preference combined with thermal-induced interfaces migration. Interface engineering is a significant strategy to develop structural materials with good properties. In this study, bulk V/Cu nano-multilayers with different layer thicknesses were fabricated by cross accumulative roll bonding (CARB). Interface stability of V/Cu nano-multilayers with different layer thicknesses and their effects on thermal conductivity and helium irradiation have been explored. The microstructure analysis, tensile and hardness tests result show that V/Cu nano-multilayers maintain high mechanical properties and good thermal stability after annealing at 500 °C for 1 h. However, the strength drastically degrades after higher-temperature annealing because of microstructure instability, which is closely related to the aspect ratio of grains. Furthermore, spheroidization occurring in multilayer during the annealing process promotes efficient electron transportation and weakens electron scattering, which benefits the increase of thermal conductivity. The irradiation response of V/Cu nano-multilayers was explored by helium bombardment with a fluence of 1 × 1017 ions/cm2 at room temperature and 500 °C, respectively. Helium bubbles transform to gas cavities with increasing irradiated temperature, and different morphology of cavities at heterointerface, newly formed grain boundaries and triple junctions is attributed to the defect diffusion preference combined with thermal-induced interfaces migration. [ABSTRACT FROM AUTHOR]