Positron annihilation lifetime spectroscopy of annealed tungsten

Abstract

Abstract Three samples of 99.97% pure rolled tungsten were annealed at 700 °C, 1000 °C, and 1400 °C in a vacuum of about 10−6 mbar for 1 h. Then the effects of annealing were investigated. For this purpose, defects and their structure in the three annealed samples and the as-received sample, were studied, characterized, and compared by the positron annihilation lifetime spectroscopy (PALS) technique. A large number of mono-vacancy and cavity defects were determined in the as-received sample. The results show that by increasing the temperature, the density, and size of the defects drastically decreased, and their structure changed to dislocation/vacancy loops. The structure and status of defects in annealed samples are almost constant. τ ave with a 40% decrease in 1400 °C compared to as-received, indicates the beginning of removing defects from tungsten at the temperature of 1400 °C.