Constitutive analysis and processing maps revealing the hot deformation mechanisms and workability of N18 zirconium alloy

The hot compression deformation behavior of the N18 zirconium alloy was systematically investigated in the temperature range of 600–800 °C and at strain rates of 0.01–5 s−1. Experimental results showed that the flow stress decreases with increasing temperature and increases with increasing strain rate. After reaching the peak stress, the flow curves exhibit pronounced flow softening, which is associated with dynamic recrystallization (DRX). An Arrhenius constitutive model was established using the peak stress data. The activation energy for hot deformation was calculated as 434.9 kJ mol−1, and the stress exponent was determined to be 7.752. Furthermore, the processing map of the N18 zirconium alloy was constructed using the Dynamic Material Model (DMM), revealing the optimal processing window to be at temperatures of 700–800 °C and strain rates from 0.01 to 0.05 s−1. Microstructural analysis revealed banded grains at low temperature and high strain rate, whereas higher temperatures promoted recrystallization and the formation of refined α/β structures.