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 tar phase. It remains quenched at the ambient pressure and disappears by heating only above 400 degrees C. The diffusion-controlled alpha Zr + beta Nb <->alpha Zr + beta Zr <->beta Zr transformations are observed only in the as-cast alloy Zr-2.5 mass% Nb. Transformation alpha Zr <->beta Zr 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 T-eff=700 degrees C at 5 GPa. (C) 2012 Elsevier B.V. All rights reserved.