Studies of metals by positron annihilation

The applications of positron annihilation to the study of metals are reviewed. The first several sections of this report introduce positron sources, the principle of gamma-gamma angle correlation, the energy spectrum of annihilation gamma-ray, the measurement of the life time of positrons, and the basic relation between lattice defects and positron annihilation. The trapping model is also explained in connection with the temperature dependence of the life time of positrons. The remaining sections of this report explain the basic concept and present the typical results obtained by various researchers in the following application areas: vacancies in pure metals, vacancies in high concentration alloys, formation of vacancies and vacancy-impurity atom pairs in dilute alloys, positron trapping by impurity atoms, regular- irregular transformation, precipitation and phase separation, martensite transformation, molten metals, alloys, solidification and amorphous metals, radiation damage and recovery, dislocation, plastic deformation and fatigue, and delayed rupture of steel. (Aoki, K.)