A detailed study of texture changes during alpha–beta processing of a zirconium alloy

Abstract

The properties and performance of Zr-2.5 Nb alloys are strongly influenced by their crystallographic texture. As in similar Ti alloys, the texture evolution during hot-processing depends on the complex interactions between the α and β phases and involves deformation, annealing and phase transformation. Although the effect of temperature and deformation has been studied for extruded tube in this alloy, there is no data for texture development during rolling. There is some rolling data for Ti-64 (Ti–6Al–4V), but it is usually for just one of the phases and for a limited set of temperatures. We carried out hot-rolling trials from 700 °C–900 °C to reductions of 50%, 75% and 87.5% and found that the texture in both phases strengthens sharply before the β-transus and when both phases are present in similar amounts. At this point, the texture in α is a strong 0002||TD and the texture in β a strong {001}〈110〉 rotated cube component. The results suggest there might be a synergistic effect between the two components, which includes dynamic phase transformation. The texture evolution towards stable α {112¯0}〈101¯0〉 or {112¯1}〈101¯0〉 crystallographic components and their final intensity depend on the starting texture. Texture was measured using electron-backscatter diffraction (EBSD) over large areas, with a β reconstruction software used to determine the high temperature β orientations. The texture development in Zr-2.5Nb appears similar to that reported for rolled Ti-64 at temperatures with equivalent phase fractions, although it is difficult to compare the two because of the lack of a titanium dataset as detailed as the one presented here.