Abstract In the current work, the high-temperature deformation behaviour of Zr-2.5Nb alloys used in pressurized heavy water reactors has been studied. Uniaxial tensile tests were carried out for both longitudinal and transverse specimen orientations in the temperature range of 25–800 °C at a nominal strain rate of 1 × 10–4 s−1. The transverse samples exhibited higher strength and lower ductility than the longitudinal ones at all temperatures. Percentage elongation of 406% and 386% was observed for the longitudinal and transverse samples, respectively, at 800 °C. The variation of tensile properties has been correlated over a wide range of temperatures by empirical equations, which will be beneficial for the computation of the elevated temperature deformation behaviour during the loss of coolant accident scenario in the reactors. TEM studies revealed the presence of Nb-enriched precipitates at the grain boundaries at elevated temperatures. The high value of strain rate sensitivity (m) obtained from the strain rate jump test in the temperature range of 600–800 °C confirmed the superplastic behaviour of this alloy in the region. The m-value and activation energy indicated that grain boundary sliding was the primary mechanism during superplastic deformation, accommodated by a combination of lattice and grain boundary diffusion.
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