Phase transformations in the severely plastically deformed Zr-Nb alloys

摘要

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 to Zr phase. It re-mains quenched at the ambient pressure and disappears by heating only above 400 ℃. 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 oc-curring in alloys of both compositions after HPT on heating are martensitic. The effective temperature during HPT has been determined as T_(eff) = 700 ℃ at 5 GPa.