Electrical resistivity study of recovery phenomena in cold-worked zirconium

The recovery of zirconium of two different purities, cold rolled to 80 % reduction at room temperature, has been followed by means of electrical resistivity measurements at −196° C. In 99.5 % zirconium, recovery proceeds mainly in two stages. The first stage (stage A1) ranging between room temperature and ~ 315° C, is characterized by an activation energy increasing linearly with recovered extra resistivity between 1.00 and 1.85 eV and obeys logarithmic kinetics; this has been attributed to a small scale dislocation rearrangement. The second stage (stage B1), centred at 475° C, is characterized by an activation energy of 2.30 ± 0.25 eV and corresponds to recrystallization. In 99.95 % zirconium, stage B1 is lowered to ~ 325° C and is characterized by an. activation energy of 1.70 ± 0.15 eV . On the other hand, the first recovery stage begins only above 100° C and is characterized by a constant activation energy of 1.35 ± 0.05 eV (stage A2). This may be reasonably attributed to point defect annealing, which probably occurs also in 99.5 % zirconium, but remains unresolved under the continuous background due to dislocation re-arrangement.