Phase Transformation and Atypical Variants in an Extruded Two Phase Zirconium Tube

The texture evolution of a Zr-2.5wt pctNb alloy pressure tube is characterized after the α → β transformation and the β → α transformation by room temperature EBSD maps and reconstruction of the high temperature β phase. The β phase forms a deformation texture which varies along the radial direction of the tube and changes after thermal cycling. Variant selection during the β → α phase transformation is shown to be strongly influenced by residual stress within the material, with a more randomized variant selection for water quenched samples. Slower cooling rates were found to create orientations in addition to the 12 α variants expected by the Burger’s orientation relationship in a given β grain.