Phase transformations in the severely plastically deformed Zr–Nb alloys

Zr–Nb alloys play the important role in the energy production of being the main material for the cladding of nuclear fuel in the nuclear power plants. Severe plastic deformation by high‐pressure torsion (HPT) leads to the strong grain refinement in Zr–Nb alloys. HPT leads also to formation of the high-pressure ωZr phase. It remains quenched at the ambient pressure and disappears by heating only above 400 °C. The diffusion-controlled αZr + βNb↔αZr + βZr↔βZr transformations are observed only in the as-cast alloy Zr–2.5 mass% Nb. Transformation αZr↔βZr in as-cast alloy Zr–8 mass% Nb occurs as martensitic. Phase transformations occurring in alloys of both compositions after HPT on heating are martensitic. The effective temperature during HPT has been determined as Teff = 700 °C at 5 GPa.

► Severe plastic deformation (SPD) by refines grains in Zr–Nb alloys.
► The high-pressure ωZr-phase is formed during SPD.
► The effective temperature during high pressure torsion at 5 GPa is 700 °C.