Achieving high strength and toughness in a Zr–2.3Nb alloy by the formation of duplex microstructure

A duplex microstructure, which displays improved strength and toughness compared with a starting Widmanstätten microstructure, was obtained in a Zr–2.3Nb alloy. The duplex microstructure was generated via plastic deformation and subsequent recrystallization annealing for no less than 30 min. Air cooling was an important factor after the recrystallization process. The duplex microstructure possesses not only excellent static mechanical properties of high tensile strength (∼746 MPa), high elongation (∼16%), and high static toughness (∼119 MJ/m3), but also high dynamic impact toughness (∼134 J/cm2) which was nearly three times as great as that of the Widmanstätten microstructure (∼48 J/cm2). The crack propagation during tension and impact fracture of the duplex microstructure are both in a ductile dimple feature, revealing an excellent static and impact toughness.

► Duplex microstructure (DM) was generated in Zr–2.3Nb alloy.
► DM was got by deformation + annealing at 850 °C for no less 30 min + air cooling.
► Tensile strength in DM is 22% higher than in Widmanstätten microstructure (WM).
► Static toughness in DM (120 MJ/m3) is higher than that in WM (99 MJ/m3).
► Dynamic impact toughness in DM (134 J/cm2) is higher than that in WM (48 J/cm2).