Hot deformation behavior of Nb-1Zr-0.1C alloy in the temperature range 700-1700 °C

Nb-1 wt%Zr-0.1 wt%C was hot deformed in vacuum in uniaxial compression to a true strain of about 0.6 in the temperature range 700-1700 °C and strain rate range 10−3-10 s−1. From the stress, temperature and strain rate data iso-strain rate sensitivity contour maps were generated. Two distinct regimes were identified in the processing map: one with zero to negative strain rate sensitivity ranging from 700 to 900 °C at all the strain rates, and second a high strain rate sensitivity domain around 1700 °C and 10−3 s−1. In the first regime shear bands were seen within grains indicating strain localization. On the basis of detailed metallographic investigation and kinetic analysis, it was established that the domain corresponding to strain rate sensitivity 0.2 is of dynamic recrystallization. At deformation conditions away from this domain the microstructure was found to be heterogeneous with some grain boundaries showing wavy nature, some small grains located at these prior grain boundaries and near absence of new grains within larger grains, suggesting partial/incomplete dynamic recrystallization. A stress exponent of five and activation volume of 200-500 b3 within this domain suggests a dislocation based mechanism during dynamic recrystallization.