Dynamic recrystallisation during hot working of Zr–2·5Nb: characterisation using processing maps

Abstract

AbstractThe characteristics of the hot deformation of Zr–2·5Nb (wt-%) in the temperature range 650–950°C and in the strain rate range 0·001–100 s−1 have been studied using hot compression testing. Two different preform microstructures: equiaxed (α+β) and β transformed, have been investigated. For this study, the approach of processing maps has been adopted and their interpretation carried out using the dynamic materials model. The efficiency of power dissipation given by [2m/(m+1)], where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of dynamic recrystallisation has been identified in the maps of equiaxed (α+β) and β transformed preforms. In the case of equiaxed (α+β), the stress–strain curves are steady state and the dynamic recrystallisation domain in the map occurs with a peak efficiency of 45% at 850°C and 0·001 s−1. On the other hand, the β transformed preform exhibits stress–strain curves with continuous flow softening....