Study on secondary phase precipitate behavior in zircaloy-2 by positron annihilation spectroscopy

Abstract

It is well established that in Zr alloys, secondary phase precipitates (SPP) have a major influence on the corrosion and mechanical properties. Thus it is important to understand the kinetics and growth of precipitates under thermal treatments. In this study, secondary phase precipitates were generated by suitable heat treatment at 800 °C and 840 °C for different duration (1-1440 minutes). Positron lifetime spectroscopy and Doppler broadening measurements were carried out to examine the nucleation and growth aspects of the precipitates. The variation in lifetime and S-parameter were seen to be consistent. From the S-W curve it is seen that the defects associated with precipitation at 800 °C and 840 °C are different. Possible mechanism for precipitation of SPP's has been proposed based on the positron annihilation data.