Positron annihilation measurement of the defects of Zr

Abstract

Positron annihilation measurement(PAM) was used to measure the annealing characteristics of variously treated zirconium. The sensitivity of PAM to variously treated specimen was studied on the purity of sample and heat treatment, respectively. The positron trapping was saturated at lower deformation level(5\%). Isochronal annealing curves of cold-worked and quenched Zr suggest that the initial rise in Doppler broadening lineshape parameter(S/W) is due to the formation of vacancy-impurity complexes in the recovery region. Recovery of these defects distinctly occurred between $200 \sim 300\,^\circ\!C$, while recrystallization occurred between $500 \sim 60\,^\circ\!C$ for cold-worked Zr. PAM was quite sensitive to changes in the recovery, whereas hardness measurement was insensitive in the region. The S/W parameter for heat-treated specimens increased with cooling rates and increasing quenching temperatures. The sensitivity of PAM to hydrogen inclusion increased with heat treatment, particularly with water quenching. it is inferred that the distribution of precipitated hydrides would make a large contribution to the saturation of positron trapping for relatively low hydrogen-dissolved specimen. PAM could be useful in evaluating the behavior of nonequilibrium defects of Zr induced by various treatments.