Thermal stable hierarchical 3D nanolayered Zr-2.5Nb

Hierarchical 3D nanolayered Zr-2.5Nb has high strength, strain hardening and ductility because of the 3D α/β-Zr networks, which is a promising structural material for nuclear reactor. However, excellent thermal stability is of great importance for materials service in nuclear reactor. Here, we study thermal stability of the hierarchical 3D nanolayered Zr-2.5Nb. After 1 h annealing at various temperatures below 700 °C, α-Zr layer thickness only has a slightly increase. The hardness, yield strength and uniform elongation of the sample remain unchanged. Interface orientation relationship and layer morphology keep stable after annealing, indicating high thermal stability. The duplex phase structures coarsen quickly after annealing at 1000 °C. An obvious increase in hardness and yield strength was observed when sample annealed at 300 °C, which relates to the precipitation of ωiso phase in β-Zr. Controlling the number of ωiso phase is likely a strategy to further enhance the strength and ductility of the alloy.