Positron annihilation measurements performed on oxide-dispersion strengthened steels

This paper is focused on investigation of oxide-dispersion strengthened steels in a basic state (before an experimental treatment) by two positron annihilation techniques - positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy. Three high chromium commercial steels - MA 956, MA 957 and PM 2000 were measured in order to identify and quantify defects in samples as well as to demonstrate defect depth profile in subsurface layers up to 1.6μm. Results indicate presence of di-vacancies in PM 2000, three-vacancies in MA 956 and six-vacancies together with dislocations in MA 957. Positron techniques were supplemented by scanning electron microscopy, which demonstrated also presence of larger defects as pores and different density of precipitates.