Mechanical properties and dynamic strain aging behavior of Zr–1.5Nb–0.4Sn–0.2Fe alloy

To elucidate the dynamic strain aging behavior of Zr–1.5Nb–0.4Sn–0.2Fe alloy which was developed as an advanced nuclear fuel cladding material, tensile tests were carried out for the alloy in the range of 25–500 °C at the strain rate of 8.33 × 10−5 and 1.67 × 10−2 s−1. The results showed that the alloy exhibited the characteristics of the dynamic strain aging behavior above 200 °C such as an increase in the strength, work hardening exponent as well as a decrease in the ductility and strain rate sensitivity. An increase of the heat treatment temperature from 470 to 510 °C shifted the temperature range of the dynamic strain aging to a higher temperature range because the initial dislocations causing the dynamic strain aging were annihilated by the heat treatment. The analysis of the activation energy and the diffusion model of the solute atom revealed that the dynamic strain aging in Zr–1.5Nb–0.4Sn–0.2Fe alloy was due to a thermal migration of vacancies generated around the substitutional solute atoms in addition to a diffusion of the interstitial solute atoms.